diff --git a/src/toucan/models.clj b/src/toucan/models.clj
index 38b3814..669a7fb 100644
--- a/src/toucan/models.clj
+++ b/src/toucan/models.clj
@@ -266,7 +266,12 @@
 
       (add-property! :timestamped?
         :insert (fn [obj] (assoc obj :created-at (new-timestamp), :updated-at (new-timestamp)))
-        :update (fn [obj] (assoc obj :updated-at (new-timestamp))))"))
+        :update (fn [obj] (assoc obj :updated-at (new-timestamp))))")
+
+  (primary-key [this]
+    "Returns a keyword that represents the primary key.
+
+     The default implementation returns `:id`"))
 
 
 ;;;                                                      INTERNAL IMPL
@@ -337,19 +342,24 @@
    :pre-update     identity
    :post-select    identity
    :pre-delete     (constantly nil)
-   :hydration-keys (constantly nil)})
+   :hydration-keys (constantly nil)
+   :primary-key    (constantly :id)})
 
 (defn- invoke-model
   "Fetch an object with a specific ID or all objects of type ENTITY from the DB.
 
      (invoke-model Database)           -> seq of all databases
-     (invoke-model Database 1)         -> Database w/ ID 1
+     (invoke-model Database 1)         -> Database w/ ID 1 (or primary-key)
      (invoke-model Database :id 1 ...) -> A single Database matching some key-value args"
   ([model]
    ((resolve 'toucan.db/select) model))
   ([model id]
    (when id
-     (invoke-model model :id id)))
+     (if (map? id)
+       (let [args (vec (flatten (into [] id)))
+             invoke-part (partial invoke-model model)]
+         (apply invoke-part args))
+       (invoke-model model (primary-key model) id))))
   ([model k v & more]
    (apply (resolve 'toucan.db/select-one) model k v more)))
 
diff --git a/test/toucan/models_test.clj b/test/toucan/models_test.clj
index 82cb333..820fe52 100644
--- a/test/toucan/models_test.clj
+++ b/test/toucan/models_test.clj
@@ -4,6 +4,7 @@
                     [models :as models])
             [toucan.test-setup :as test]
             (toucan.test-models [category :refer [Category], :as category]
+                                [inventory :refer [Inventory map->InventoryInstance]]
                                 [user :refer [User]]
                                 [venue :refer [Venue map->VenueInstance]])
             [toucan.util.test :as tu]))
@@ -177,3 +178,13 @@
 (expect
  #toucan.test_models.venue.VenueInstance{}
  (empty (Venue :name "BevMo")))
+
+;; Test using a primary key other than `id`
+(expect
+ #toucan.test_models.inventory.InventoryInstance{:name "Computer", :sku "cp-1" :id 1}
+ (Inventory "cp-1"))
+
+;; Test using multiple keys as a fake primary
+(expect
+ #toucan.test_models.inventory.InventoryInstance{:name "Computer", :sku "cp-1" :id 1}
+ (Inventory {:sku "cp-1" :name "Computer"}))
diff --git a/test/toucan/test_models/inventory.clj b/test/toucan/test_models/inventory.clj
new file mode 100644
index 0000000..817c39e
--- /dev/null
+++ b/test/toucan/test_models/inventory.clj
@@ -0,0 +1,9 @@
+(ns toucan.test-models.inventory
+  "A model with `:primary-key` set to `sku`"
+  (:require [toucan.models :as models]))
+
+(models/defmodel Inventory :inventories)
+
+(extend (class Inventory)
+  models/IModel
+  (merge models/IModelDefaults {:primary-key    (constantly :sku)}))
diff --git a/test/toucan/test_setup.clj b/test/toucan/test_setup.clj
index 55b6bf7..61f0c46 100644
--- a/test/toucan/test_setup.clj
+++ b/test/toucan/test_setup.clj
@@ -5,6 +5,7 @@
             (toucan [db :as db]
                     [models :as models])
             (toucan.test-models [category :refer [Category]]
+                                [inventory :refer [Inventory]]
                                 [user :refer [User]]
                                 [venue :refer [Venue]])
             [toucan.util.test :as u])
@@ -52,7 +53,13 @@
        name VARCHAR(256) UNIQUE NOT NULL,
        \"parent-category-id\" INTEGER
      );"
-    "TRUNCATE TABLE categories RESTART IDENTITY CASCADE;"))
+    "TRUNCATE TABLE categories RESTART IDENTITY CASCADE;"
+    ;; Inventory
+    "CREATE TABLE IF NOT EXISTS inventories (
+      id SERIAL PRIMARY KEY,
+      sku VARCHAR(256) UNIQUE NOT NULL,
+      name VARCHAR(256) NOT NULL);"
+    "TRUNCATE TABLE inventories RESTART IDENTITY CASCADE;"))
 
 (def ^java.sql.Timestamp jan-first-2017 (Timestamp/valueOf "2017-01-01 00:00:00"))
 
@@ -72,7 +79,12 @@
     [{:name "bar"}
      {:name "dive-bar", :parent-category-id 1}
      {:name "resturaunt"}
-     {:name "mexican-resturaunt", :parent-category-id 3}]))
+     {:name "mexican-resturaunt", :parent-category-id 3}])
+  ;; Inventory
+  (db/simple-insert-many! Inventory
+    [{:name "Computer" :sku "cp-1"}
+     {:name "Text Book" :sku "tb-1"}
+     {:name "Pencils" :sku "pn-1"}]))
 
 (defn reset-db!
   "Reset the DB to its initial state, creating tables if needed and inserting the initial test data."