Blood samples were taken from 47 clinically normal, wild-born Eurasian otters (Lutra lutra) before they were released from a rehabilitation centre in Scotland between August 1990 and March 1996. Serum biochemistry profiles were determined for 47 animals and haematological profiles for 41, and the results from males, females, and animals under or over one year of age were analysed as separate groups and as pooled populations. The normal ranges for a wide variety of haematological and serum biochemical parameters of the Eurasian otter are presented, and significant differences with age and sex are detailed.