Sixteen separate hematologic and twelve chemical analyses were performed on a total of 93 sera from adult wild sea otters and 23 sera from juvenile wild sea otters. The mean, standard deviation, range and coefficient of variation are presented for the adult and juvenile groups as a whole and for the following subgroups: restraint with anesthesia vs. restraint without anesthesia, adult male vs. female, capture with dip net vs. Wilson trap, juvenile male vs. female, juveniles less than three weeks of age vs. juveniles between 3 and 6 weeks of age. Statistically significant differences between mean values of the various pairs of subgroups were uncommon. Due to the large number of individual comparisons, a few statistically significant differences were likely to occur by chance alone and no special clinical significance can be attributed to their occurrence. However, when mean values for adults were compared to mean values for juveniles: real differences were found. Hematocrits, red cell counts, and hemoglobins in juveniles were consistently low when compared to adults. White cell counts were also somewhat lower in juveniles.