diff --git a/panaroo/__main__.py b/panaroo/__main__.py
index 5ffb6a2..78bc8f1 100755
--- a/panaroo/__main__.py
+++ b/panaroo/__main__.py
@@ -235,6 +235,11 @@ def get_options(args):
                       help="Core-genome sample threshold (default=0.95)",
                       type=float,
                       default=0.95)
+    core.add_argument("--core_subset",
+                      dest="subset",
+                      help="Subset the core genome to these many random genes (default=all)",
+                      type=int,
+                      default=None)
     core.add_argument("--core_entropy_filter",
                       dest="hc_threshold",
                       help=("Manually set the Block Mapping and Gathering with " +
@@ -512,7 +517,7 @@ def main():
         generate_core_genome_alignment(G, temp_dir, args.output_dir,
                                        args.n_cpu, args.alr, isolate_names,
                                        args.core, args.codons, len(args.input_files),
-                                       args.hc_threshold)
+                                       args.hc_threshold, args.subset)
 
     # remove temporary directory
     shutil.rmtree(temp_dir)
diff --git a/panaroo/generate_output.py b/panaroo/generate_output.py
index c65cbb1..928538b 100755
--- a/panaroo/generate_output.py
+++ b/panaroo/generate_output.py
@@ -9,6 +9,7 @@
 from Bio.SeqRecord import SeqRecord
 import itertools as iter
 from tqdm import tqdm
+import random
 
 from .generate_alignments import *
 
@@ -321,12 +322,18 @@ def generate_pan_genome_alignment(G, temp_dir, output_dir, threads, aligner,
     return
 
 
-def get_core_gene_nodes(G, threshold, num_isolates):
+def get_core_gene_nodes(G, threshold, num_isolates, subset=None):
     # Get the core genes based on percent threshold
     core_nodes = []
     for node in G.nodes():
         if float(G.nodes[node]["size"]) / float(num_isolates) >= threshold:
             core_nodes.append(node)
+    if subset is not None:
+        if subset > len(core_nodes):
+            raise RuntimeError(f"Cannot subset core genes to {subset}, "
+                               f"only {len(core_nodes)} are available!")
+        random.shuffle(core_nodes)
+        core_nodes = core_nodes[:subset]
     return core_nodes
 
 def update_col_counts(col_counts, s):
@@ -431,7 +438,8 @@ def concatenate_core_genome_alignments(core_names, output_dir, hc_threshold):
 
 
 def generate_core_genome_alignment(
-    G, temp_dir, output_dir, threads, aligner, isolates, threshold, codons, num_isolates, hc_threshold
+    G, temp_dir, output_dir, threads, aligner, isolates, threshold, codons, num_isolates, hc_threshold,
+    subset=None
 ):
     # Make a folder for the output alignments TODO: decide whether or not to keep these
     try:
@@ -439,10 +447,11 @@ def generate_core_genome_alignment(
     except FileExistsError:
         None
     # Get core nodes
-    core_genes = get_core_gene_nodes(G, threshold, num_isolates)
+    core_genes = get_core_gene_nodes(G, threshold, num_isolates, subset)
     if len(core_genes) < 1:
         print("No gene clusters were present above the core frequency"
               " threshold! Try adjusting the '--core_threshold' parameter")
+        return
 
     core_gene_names = [G.nodes[x]["name"] for x in core_genes]
 
diff --git a/panaroo/merge_graphs.py b/panaroo/merge_graphs.py
index e54e9b4..70fc7ab 100644
--- a/panaroo/merge_graphs.py
+++ b/panaroo/merge_graphs.py
@@ -264,6 +264,7 @@ def merge_graphs(directories,
                  alr,
                  core,
                  hc_threshold,
+                 subset=None,
                  merge_single=False,
                  depths=[1,2,3],
                  n_cpu=1,
@@ -431,7 +432,7 @@ def merge_graphs(directories,
         if not quiet: print("generating core genome MSAs...")
         generate_core_genome_alignment(G, temp_dir, output_dir, n_cpu, alr,
                                        isolate_names, core, len(isolate_names), 
-                                       hc_threshold)
+                                       hc_thresholdi, subset)
     return
 
 
@@ -533,6 +534,11 @@ def get_options():
                       help="Core-genome sample threshold (default=0.95)",
                       type=float,
                       default=0.95)
+    core.add_argument("--core_subset",
+                      dest="subset",
+                      help="Subset the core genome to these many random genes (default=all)",
+                      type=int,
+                      default=None)
     core.add_argument("--core_entropy_filter",
                       dest="hc_threshold",
                       help=("Manually set the Block Mapping and Gathering with " +
diff --git a/panaroo/post_run_alignment_gen.py b/panaroo/post_run_alignment_gen.py
index 1b42f4b..c8450cc 100755
--- a/panaroo/post_run_alignment_gen.py
+++ b/panaroo/post_run_alignment_gen.py
@@ -55,6 +55,11 @@ def get_options():
                       help="Core-genome sample threshold (default=0.95)",
                       type=float,
                       default=0.95)
+    core.add_argument("--core_subset",
+                      dest="subset",
+                      help="Subset the core genome to these many random genes (default=all)",
+                      type=int,
+                      default=None)
     core.add_argument("--core_entropy_filter",
                       dest="hc_threshold",
                       help=("Manually set the Block Mapping and Gathering with " +
@@ -114,7 +119,7 @@ def main():
         generate_core_genome_alignment(G, temp_dir, args.output_dir,
                                        args.n_cpu, args.alr, isolate_names,
                                        args.core, args.codons, len(isolate_names),
-                                       args.hc_threshold)
+                                       args.hc_threshold, args.subset)
 
     # remove temporary directory
     shutil.rmtree(temp_dir)