1. Standard laboratory values of blood samples taken from Weddell seals in Antarctica were determined. 2. Numerous blood parameters are similar to those observed in man. 3. Comparatively high cholesterol levels but normal triglyceride levels were observed when compared with humans. 4. In comparison to laboratory findings in humans, T4 levels were decreased although T3 levels were normal. 5. The levels of alkaline phosphatase are considerably higher than those in humans. 6. The data obtained indicate different lipid and thyroid hormone metabolism in Weddell seals when compared with humans.