diff --git a/libs/cyclone/concurrent.sld b/libs/cyclone/concurrent.sld
index 4b735bb8..54364954 100644
--- a/libs/cyclone/concurrent.sld
+++ b/libs/cyclone/concurrent.sld
@@ -24,6 +24,12 @@
    swap!
    compare-and-set!
    atom-deref
+   ;; Delays
+   make-shared-delay
+   shared-delay
+   ;; Promises
+   make-shared-promise
+   deliver
    ;; Futures
    future?
    future
@@ -62,16 +68,17 @@
   (cond
     ((atom? obj) (atom-deref obj))
     ((future? obj) (future-deref obj))
+    ((shared-delay? obj) (shared-delay-deref obj))
+    ((shared-promise? obj) (shared-promise-deref obj))
     ((shared-queue? obj) (shared-queue-remove! obj))
     (else obj)))
 
-;; TODO: (realized? obj) - see clojure docs
-;; Returns true if a value has been produced for a promise, delay, future or lazy sequence.
+;; Returns true if a value has been produced for a promise, delay, or future.
 (define (realized? obj)
   (cond
-    ;; TODO: ((future? obj) (future-done? obj))
-    ;; TODO: ((shared-delay? obj) (shared-delay-realized? obj))
-    ;; TODO: ((shared-promise? obj) (shared-promise-realized? obj))
+    ((future? obj) (future-done? obj))
+    ((shared-delay? obj) (shared-delay-realized? obj))
+    ((shared-promise? obj) (shared-promise-realized? obj))
     (else #f)))
 
 (define-c atom?
@@ -190,6 +197,87 @@
    }
    return_closcall1(data, k, result); ")
 
+;; Delays
+(define-record-type <shared-delay>
+  (%make-shared-delay done result lock)
+  shared-delay?
+  (done sd:done sd:set-done!)
+  (value sd:value sd:set-value!) ;; Either thunk or result
+  (lock sd:lock sd:set-lock!))
+
+(define (make-shared-delay thunk)
+  (make-shared 
+    (%make-shared-delay #f thunk (make-mutex))))
+
+(define (shared-delay-deref d)
+  (when (not (shared-delay? d))
+    (error "Expected future but received" d))
+  (mutex-lock! (sd:lock d))
+  (cond
+    ((sd:done d) 
+     (sd:value d))
+    (else
+     (sd:set-value! d 
+       (make-shared ((sd:value d)))) ;; Exec thunk and store result
+     (sd:set-done! d #t)))
+  (mutex-unlock! (sd:lock d))
+)
+
+(define (shared-delay-realized? obj)
+  (let ((rv #f))
+    (mutex-lock! (sd:lock obj))
+    (set! rv (sd:done obj))
+    (mutex-unlock! (sd:lock obj))
+    rv))
+
+(define-syntax shared-delay
+  (er-macro-transformer
+   (lambda (expr rename compare)
+     `(make-shared-delay (lambda () ,(cadr expr))))))
+
+;; Promises
+
+(define-record-type <shared-promise>
+  (%make-shared-promise done value lock cv)
+  shared-promise?
+  (done sp:done sp:set-done!)
+  (value sp:value sp:set-value!)
+  (lock sp:lock sp:set-lock!)
+  (cv sp:cv sp:set-cv!))
+
+(define (make-shared-promise)
+  (make-shared
+    (%make-shared-promise #f #f (make-mutex) (make-condition-variable))))
+
+;; Blocks until given promise has a value, and returns that value.
+(define (shared-promise-deref obj)
+  (when (not (shared-promise? obj))
+    (error "Expected shared promise but received" obj))
+  (mutex-lock! (sp:lock obj))
+  (if (sp:done obj)
+      (mutex-unlock! (sp:lock obj))
+      (mutex-unlock! (sp:lock obj) (sp:cv obj))) ;; wait until value is ready
+  (sp:value obj))
+
+(define (shared-promise-realized? obj)
+  (let ((rv #f))
+    (mutex-lock! (sp:lock obj))
+    (set! rv (sp:done obj))
+    (mutex-unlock! (sp:lock obj))
+    rv))
+
+;; Delivers `value` to shared promise `obj` and unblocks waiting threads.
+;; Has no effect if a value has already been delivered.
+(define (deliver obj value)
+  (when (not (shared-promise? obj))
+    (error "Expected shared promise but received" obj))
+  (mutex-lock! (sp:lock obj))
+  (when (not (sp:done obj))
+    (sp:set-value! obj (make-shared value)) 
+    (sp:set-done! obj #t))
+  (mutex-unlock! (sp:lock obj))
+  (condition-variable-broadcast! (sp:cv obj)))
+
 ;; Futures
   (define-record-type <future>
     (make-future done result lock)