diff --git a/CircularBuffer/CircularBuffer.c b/CircularBuffer/CircularBuffer.c
index 5db54b1..9d6aa99 100644
--- a/CircularBuffer/CircularBuffer.c
+++ b/CircularBuffer/CircularBuffer.c
@@ -10,8 +10,24 @@
 CircularBuffer * circularbuffer_initialize(size_t size, void * val){
 	size_t i;
 	CircularBuffer * cb = (CircularBuffer *)malloc( sizeof(CircularBuffer) );
+        
+        if (cb == NULL) {
+            
+            // any other implementation may be added here.
+            
+            printf("\nERROR: Insufficient memory. Terminating...");
+            exit(EXIT_FAILURE);
+        }
 
 	cb->buffer = (Item *)calloc(size, sizeof(Item));
+        
+        if (cb->buffer == NULL) {
+            
+            // any other implementation may be added here.
+            
+            printf("\nERROR: Insufficient memory. Terminating...");
+            exit(EXIT_FAILURE);
+        }
 
 	for(i=0; i<size; i++){
 		cb->buffer[i].data = val;
diff --git a/HashTable/HashTable.c b/HashTable/HashTable.c
index 0a6ceac..4ffda85 100644
--- a/HashTable/HashTable.c
+++ b/HashTable/HashTable.c
@@ -17,6 +17,11 @@
 HashTable * hashtable_initialize(size_t size, size_t mc, size_t gf, hash_function fn, compare_equal efn){
 	size_t i;
 	HashTable * ht = (HashTable *) malloc( sizeof(HashTable) );
+        
+        if (ht == NULL) {
+            printf("\nERROR: Cannot create hash table. Terminating...");
+            exit(EXIT_FAILURE); // well... any other implementation could be added, instead of this.
+        }
 
 	ht->hf = fn;
 	ht->eq = efn;
@@ -25,6 +30,11 @@ HashTable * hashtable_initialize(size_t size, size_t mc, size_t gf, hash_functio
 	ht->growthFactor = gf;
 
 	ht->table = (Item **) malloc(size * sizeof( Item * ));
+        
+        if (ht->table == NULL) {
+            printf("\nERROR: Cannot create hash table. Terminating...");
+            exit(EXIT_FAILURE); // well... any other implementation could be added, instead of this.
+        }
 
 	for(i=0; i<size; i++){
 		ht->table[i] = 0;
@@ -49,8 +59,19 @@ void * hashtable_get(HashTable * ht, void * key){
 }
 
 int hashtable_destroy(HashTable * ht){
+    
+        // Avoiding runtime errors. Return a successful destroy when the 
+        // hashtable has not been initialized using the 'hashtable_initialize'
+        // function.
+    
+        if (ht == NULL)                 
+          return 1;
+        
+        // From here we know the hashtable has been properly initialized so, 
+        // we continue computations.
+        
 	size_t i;
-
+        
 	for(i=0; i<ht->size; i++){
 		free(ht->table[i]);
 	}
@@ -79,8 +100,8 @@ int hashtable_resize(HashTable * ht, size_t size){
 	}
 
 	free(ht->table);
-	ht->size = newht->size;
-	ht->table = newht->table;
+	newht->size = ht->size;
+	newht->table = ht->table;
 
 	return(1);
 }
@@ -102,6 +123,13 @@ int hashtable_add(HashTable * ht, void * key, void * value){
 	}
 
 	next = (Item *)malloc( sizeof(Item) );
+        
+        // Making sure that memory was properly allocated for 'next'.
+        if (next == NULL) {
+            printf("\nERROR: Insufficient memory. Terminating....");
+            exit(EXIT_FAILURE); // some other implementation could be used here.
+        }
+        
 	next->key = key;
 	next->value = value;
 	next->next = ht->table[ hash % ht->size ];
diff --git a/List/ListItem.c b/List/ListItem.c
index d289be5..28045c8 100644
--- a/List/ListItem.c
+++ b/List/ListItem.c
@@ -12,6 +12,13 @@
  */
 ListItem_t * list_item_initialize(){
 	ListItem_t * li = (ListItem_t *) malloc( sizeof(ListItem_t) );
+        
+        // Making sure there was enough memory for a 'ListItem_t' type 'li'.
+        if (li == NULL) {
+            printf("\nERROR: Insufficient memory. Terminating...");
+            exit(EXIT_FAILURE);   
+        }
+        
 	li->next = 0;
 
 	return(li);
diff --git a/Queue/Queue.c b/Queue/Queue.c
index fe17028..a7a6373 100644
--- a/Queue/Queue.c
+++ b/Queue/Queue.c
@@ -20,11 +20,19 @@ int queue_push(Queue_t * q, void * d){
 
 	if(q->size == 0){
 		q->head = (QueueItem_t *) malloc( sizeof(QueueItem_t) );
+                if (q->head == NULL) {
+                    printf("\nERROR: Insufficient memory. Terminating...");
+                    exit(EXIT_FAILURE);
+                }
 		q->head->next = 0;
 		q->head->data = d;
 	}else{
 		tmp = q->head;
 		q->head = (QueueItem_t *) malloc( sizeof(QueueItem_t) );
+                if (q->head == NULL) {
+                    printf("\nERROR: Insufficient memory. Terminating...");
+                    exit(EXIT_FAILURE);
+                }
 		q->head->data = d;
 		q->head->next = tmp;
 	}