A review of the world literature until December 1982 revealed 843 cases of sulphonylurea-induced hypoglycaemia (SIH) with a mortality of 9%. There were 42 cases of metformin-associated lactic acidosis (MALA) with 18 deaths (43%); 40 of the MALA cases had documented contra-indications, especially renal impairment, and the remaining two cases were due to drug overdosage, one being a suicide. A comparative mortality risk was obtained from the Swedish Adverse Drug Reactions Advisory Committee (SADRAC) where there is accurate information regarding MALA and glibenclamide-associated hypoglycaemia. The calculated mortality risk for MALA and glibenclamide-associated hypoglycaemia showed no significant differences with values of 0.0240 and 0.0332 per 1,000 patient years, respectively. The incidence of hypoglycaemia with glibenclamide was greater than that of lactic acidosis associated with metformin (2p = 0.036). Sulphonylureas are not less dangerous than metformin and both groups of drugs should be used with care in non-insulin-dependent diabetics, especially in alderly subjects and those with impaired renal or hepatic function.