Subcutaneous injection of sodium dichromate into male Sprague-Dawley rats immediately produced a variety of metabolic changes in a dose-dependent manner. Serum lactate and glucose were significantly increased after dichromate treatment, reaching maximum levels at 15 and 30 min, respectively. Then, the toxicity progressively diminished. In contrast, a steady increase in blood urea nitrogen (BUN) concentration was caused by dichromate, reaching maximum levels at 60 min after the administration; elevated BUN levels were sustained for several hours thereafter. Unlike KCN (5 mg/kg, ip) and As2O3 (5 mg/kg, ip), dichromate rapidly decreased serum insulin within 15 min after intoxication in doses of 20 and 40 mg/kg; hypoinsulinemia lasted 60 min. However, insulin levels returned to the normal range at 120 min after treatment. Dichromate-induced metabolic disturbance was also observed in the 24 hr-fasted rats, the response of which was similar to normal rats except for later hyperglycemia. In both cases, the duration time was short (30 to 60 min). Adrenalectomy and insulin pretreatment had no effect on dichromate-induced hyperglycemia. These results suggest that dichromate-induced metabolic disturbance results from the concomitant effects of a sudden decrease in serum insulin level and its direct inhibitory effect on carbohydrate metabolism. In addition, the characteristic biphasic pattern of metabolic disturbance might be related to metabolic fate of dichromate in vivo.