Alcohol may provoke reactive hypoglycaemia when drunk with a sucrose mixer ('gin and tonic') but does not do so when taken in the form of a starch-based beverage like sorghum beer. We examined the hypoglycaemic potential of bottled beer (Lion Lager; South African Breweries), which differs from sorghum beer in that it contains less carbohydrate (polysaccharides and simple sugars) and has a higher alcohol content. After an overnight fast 5 Black men each drank 2 litres of Lion Lager over an hour. Over the ensuing 5 hours their plasma insulin, glucose and alcohol concentrations were compared with the responses previously documented before and after consuming the same volume of sorghum beer or a 100 g control carbohydrate solution. Bottled beer elicited a prompt but short-lived rise in plasma insulin (mean +/- SEM, 37 +/- 7 mU/l at 1 hour), which was significantly greater than that produced by sorghum beer but less sustained than after drinking the control carbohydrate solution. After drinking bottled beer plasma glucose levels fell to a mean nadir of 3,6 mmol/l at 2 hours (compared with 5,4 mmol/l for sorghum beer), thereafter slowly returning to the basal value, while a substantial rise in the blood alcohol concentration occurred. We conclude that the development of alcohol-induced reactive hypoglycaemia is largely determined by the nature of the carbohydrate ingested together with alcohol.