The effects of an intraperitoneal nickel load upon plasma glucose, urea, amino acids, lactate and glucagon, as well as upon liver glycogen have been determined in 12- and 19-day pregnant rats compared with controls. Nickel induced considerable increases in both glucose and glucagon levels, delayed in 19-day pregnant rats with respect to controls, and deep and permanent decreases in glycogen and amino acids in pregnant rats. The effects of glucagon are related to the insulin resistance of pregnant rats and a relationship between nickel toxicity and the lacking capacity to recover the basal values of some parameters is suggested.