diff --git a/Cargo.toml b/Cargo.toml
index 2cea98b..351a9bc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,3 +16,6 @@ name = "rustsec-advisory-db"
 gumdrop = "0.4"
 gumdrop_derive = "0.4"
 rustsec = "0.9"
+reqwest = "0.9"
+serde = "1.0"
+serde_derive = "1.0"
diff --git a/src/main.rs b/src/main.rs
index b743605..b469a41 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,11 @@
 extern crate gumdrop;
 #[macro_use]
 extern crate gumdrop_derive;
+extern crate reqwest;
 extern crate rustsec;
+extern crate serde;
+#[macro_use]
+extern crate serde_derive;
 
 use gumdrop::Options;
 use rustsec::{AdvisoryDatabase, Repository};
@@ -65,21 +69,64 @@ fn check() {
     let repo = Repository::open(".").unwrap();
 
     // Ensure Advisories.toml parses
-    let advisory_count = AdvisoryDatabase::from_repository(&repo)
-        .unwrap()
-        .advisories()
-        .count();
+    let db = AdvisoryDatabase::from_repository(&repo).unwrap();
+    let advisories = db.advisories();
 
     // Ensure we're parsing some advisories
-    if advisory_count > MIN_EXPECTED_ADVISORIES {
+    if advisories.len() > MIN_EXPECTED_ADVISORIES {
         println!(
             "*** Check succeeded! Successfully parsed {} advisories.",
-            advisory_count
+            advisories.len()
         );
     } else {
         panic!(
             "Missing advisories! Expected at least {}, but got {}",
-            MIN_EXPECTED_ADVISORIES, advisory_count
+            MIN_EXPECTED_ADVISORIES,
+            advisories.len()
+        );
+    }
+
+    let http_client = reqwest::Client::new();
+    for advisory in advisories {
+        check_advisory(&http_client, advisory);
+    }
+    println!("*** Check succeeded! All advisories refer to valid crates.");
+}
+
+#[derive(Deserialize)]
+struct CratesResponse {
+    #[serde(rename = "crate")]
+    krate: Crate,
+}
+
+#[derive(Deserialize)]
+struct Crate {
+    name: String,
+}
+
+fn check_advisory(http_client: &reqwest::Client, advisory: &rustsec::Advisory) {
+    let mut response = http_client
+        .get(&format!(
+            "https://crates.io/api/v1/crates/{}",
+            advisory.package.as_str()
+        ))
+        .send()
+        .expect("Failed to make HTTP request to crates.io");
+    if !response.status().is_success() {
+        panic!(
+            "crates.io returned an HTTP error ({}) trying to lookup the crate '{}', does it exist?",
+            response.status(),
+            advisory.package.as_str()
+        );
+    }
+
+    let parsed_response = response
+        .json::<CratesResponse>()
+        .expect("Failed to parse crates.io response as JSON");
+    if parsed_response.krate.name != advisory.package.as_str() {
+        panic!(
+            "crates.io package name does not match package name in advisory for {}",
+            advisory.package.as_str()
         );
     }
 }