diff --git a/Cargo.toml b/Cargo.toml
index 65c96332..3dd65457 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -19,3 +19,4 @@ lalrpop-util = "0.19"
 regex = "1"
 sexp = "1.1"
 thiserror = "1.0"
+walkdir = "2"
diff --git a/README.md b/README.md
index 18a17dda..c7e72d08 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,9 @@ on the secilc package.
 
 ## casc
 The Cascade compiler is named casc, and will be located at target/debug/casc after a
-successful build.  It takes one argument, the name of a policy file to be built:
+successful build.  Input files are supplied as arguments.  Directory arguments
+are searched recursively for policy files.  If no valid policy files are found,
+casc will exit with an error.
 
 ```
 $ casc my_policy.cas
diff --git a/src/bin/casc.rs b/src/bin/casc.rs
index 58053c45..ec6bde4c 100644
--- a/src/bin/casc.rs
+++ b/src/bin/casc.rs
@@ -6,19 +6,37 @@ use selinux_cascade::error::ErrorItem;
 use clap::Parser;
 use std::fs::File;
 use std::io::{Error, ErrorKind, Write};
+use walkdir::WalkDir;
 
 #[derive(Parser, Debug)]
-#[clap(author, version, name = "casc")]
+#[clap(author, version, name = "casc", about)]
 struct Args {
+    /// List of input files to process.  Directories are searched recursively.
     #[clap(required(true))]
     input_file: Vec<String>,
 }
 
 fn main() -> std::io::Result<()> {
     let args = Args::parse();
-    let policies: Vec<&str> = args.input_file.iter().map(|s| s as &str).collect();
+    let policies: Vec<String> = match get_policy_files(args.input_file) {
+        Ok(mut s) => {
+            s.sort_unstable();
+            s
+        }
+        Err(e) => {
+            eprintln!("{}", e);
+            return Err(e);
+        }
+    };
+    if policies.is_empty() {
+        // Files supplied on command line, but no .cas files found
+        return Err(Error::new(
+            ErrorKind::InvalidData,
+            "No policy source files found",
+        ));
+    }
     let mut out_file = File::create("out.cil")?;
-    let res = compile_system_policy(policies);
+    let res = compile_system_policy(policies.iter().map(|s| s as &str).collect());
     match res {
         Err(error_list) => {
             for e in error_list {
@@ -35,3 +53,19 @@ fn main() -> std::io::Result<()> {
         Ok(s) => out_file.write_all(s.as_bytes()),
     }
 }
+
+// Create a list of policy files
+fn get_policy_files(filenames: Vec<String>) -> Result<Vec<String>, Error> {
+    let mut policy_files = Vec::new();
+    for file in filenames {
+        for entry in WalkDir::new(file) {
+            let entry = entry?;
+            if entry.file_type().is_file() && entry.path().extension().unwrap_or_default() == "cas"
+            {
+                let filename = entry.path().display().to_string();
+                policy_files.push(filename);
+            }
+        }
+    }
+    Ok(policy_files)
+}