Hepatocytes isolated from 48-hour, fasted guinea-pigs were incubated with glucose precursors to compare relative rates of glucose production. Glucose production from lactate and pyruvate was similar (2.61 vs 3.18 mumol/hr per 100 mg wet weight). Glucose production from fructose was greater than that from sorbitol (4.68 vs 1.63 mumol/hr per 100 mg wet weight). When ethanol was added to pyruvate-containing buffer, the flux of pyruvate to glucose and lactate was synergistically enhanced (5.28 vs 3.76 and 7.51 vs 2.88 mumol/hr per 100 mg wet weight, respectively). When sorbitol was added to buffer containing pyruvate, glucose and lactate production were even greater than that seen with ethanol (8.32 vs 5.38 and 15.99 vs 7.51 mumol/hr per 100 mg wet weight, respectively).