When the new Erie County Medical Center (Buffalo, NY) was built, a pneumatic tube network, manufactured by Mosler Airmatic and Electronic Systems Company, was installed. This network, called the Mosler System 4000, was designed to handle 600 transactions per hour in the hospital, and therefore had to have a high carrier speed (8m/sec). When blood specimens were sent through the system, blood cells were slightly damaged and lactic dehydrogenase activity in the serum was consistently elevated. But neither acidic phosphatase, potassium, blood gases nor urinary casts were significantly affected by tube transport.