We report the biochemical results in 90 women presenting to an eating disorders clinic: 61 who had bulimia, 22 with anorexia nervosa and seven unclassified. The results were compared with 30 control women. The group of women with an eating disorder had significantly higher concentrations of total CO2, calcium, AST, ALT, ALP, albumin and cholesterol and significantly lower concentrations of potassium, chloride and phosphate in the plasma. The elevated calcium could be accounted for in part by an increase in total CO2 and an increase in albumin. Hypokalaemia was strongly associated with self-induced vomiting and laxative abuse. Biochemical abnormalities occurred in both forms of eating disorders; however, hypercholesterolaemia was more common in anorexia nervosa and abnormal liver enzymes were more common in bulimia.