L-arabinose selectively inhibits intestinal sucrase activity in vitro and suppresses the glycaemic response in a dose-dependent manner in experimental animals. In the present study, we investigated the effect of L-arabinose on the glycaemic response of healthy volunteers and patients with type 2 diabetes. In the first experiment using a cross-over design, eight fasted normal volunteers were each given 50 g of sucrose with and without 2 g of L-arabinose. The increases in plasma glucose and serum insulin were significantly lower in the individuals given both L-arabinose and sugar. In the second experiment, the dose-dependency of L-arabinose was evaluated. Forty normal volunteer over 40 years old were given a jelly containing 30 g of sucrose with added L-arabinose in ratios of 0%, 2%, 3% and 4% (w/w) (n=10). L-arabinose at 3% significantly suppressed the increase of plasma glucose at 30 minutes after ingestion. In the third experiment, patients with type 2 diabetes (n=10) were given the jelly with 3% (w/w) added L-arabinose using a cross-over design. L-arabinose suppressed the maximal increase of plasma glucose after sucrose ingestion. These results demonstrate that L-arabinose attenuates sucrose-induced hyperglycaemia both in normal subjects and diabetic patients, presumably through inhibition of intestinal sucrase activity.