The results of sending specimens through a computerized pneumatic airtransport system and manually delivering specimens were compared for 15 chemical tests and six hematologic procedures. All specimens were collected from inpatients and outpatients into evacuated glass containers. The specimens traversed a maximum of 829 feet (253 meters) involving 16 bends and eight transfer units at 25 feet/second (7.6 meters/second). Only the activity of lactate dehydrogenase exceeded the precision of the test in pneumatically transported specimens. Ruptured erythrocytes in incompletely filled vacuum tubes were the likely source of the increased lactate dehydrogenase activity. Neither the serum sodium, potassium, chloride, carbon dioxide, total protein, albumin, calcium, glucose, creatinine, total bilirubin, alkaline phosphatase, aspartate transaminase, acid phosphatase, uric acid, leukocyte count, erythrocyte count, hemoglobin, hematocrit, nor the prothrombin time and partial thromboplastin time were affected by pneumatic transport. It is concluded that the pneumatic system tested provides a safe, efficient method of transporting the blood specimens tested.