The fasting and postprandial serum concentrations of bile acids and other blood constituents were measured in a group of 10 clinically healthy, female, six-year-old captive red-eared terrapins (Trachemys scripta elegans). The terrapins were housed in a temperate room and maintained in four aquaria in which the water temperature ranged from 24 to 27°C and the temperature above the basking site ranged from 27 to 30°C. The serum concentrations of bile acids were measured four times in a period of five months, and at the second sampling the fasting and two postprandial (after 24 and 48 hours) serum concentrations of total protein, albumin, glucose, uric acid, cholesterol, triglycerides, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and bile acids were determined. Coelioscopy revealed vitellogenic and previtellogenic follicles on the ovaries of all the terrapins, and eggs with calcified shells were detected in two of them. The livers were mostly pink to deep yellow in colour, with sharp edges, a smooth serosal surface, distinct large superficial vessels, and multifocal melanin deposits. Liver biopsies revealed fine, more or less oil red O-positive lipid droplets in all the hepatocytes, but in none of the cases was it considered to be pathological lipidosis. The mean (sd) bile acid concentrations ranged from 7·35 (4·52) to 10·04 (7·40) μmol/l. The fasting and postprandial concentrations were 3·1 (2·3), 4·5 (5·4) (24 hours) and 2·2 (1·5) (48 hours) μmol/l. High concentrations between 27·6 and 66·6 μmol/l were associated with lipaemia. There were no significant differences between the biochemical profiles of the fasting and postprandial serum samples.