Eight men with untreated type II diabetes were given 480 mL water containing 15 g, 25 g, 35 g, and 50 g fructose orally, in random sequence. The same subjects were given the same volume of water as a control. They also were given 50 g glucose on two occasions for comparative purposes. Plasma glucose, urea nitrogen, and glucagon, and serum insulin, C-peptide, alpha-amino-nitrogen (AAN), nonesterified fatty acids (NEFA), and triglycerides were determined over the subsequent 5-hour period. The area responses to each dose of fructose were calculated and compared with the water control. The integrated glucose area dose-response was curvilinear, with little increase in glucose until 50 g fructose was ingested. With the 50-g dose, the area response was 25% of the response to 50 g glucose. The insulin response also was curvilinear, but the curve was opposite to that of the glucose curve. Even the smallest dose of fructose resulted in a relatively large increase in insulin, and a near-maximal response occurred with 35 g. The area response to 50 g fructose was 39% of that to 50 g glucose. The C-peptide data were similar to the insulin data. The AAN area response to fructose ingestion was negative. However, the response was progressively less negative with increasing doses. The glucagon area response was positive, but a dose-response relationship was not apparent. The glucagon area response was negative after glucose ingestion, as expected. The urea nitrogen area response was negative, but again, a dose-response relationship to fructose ingestion was not present.(ABSTRACT TRUNCATED AT 250 WORDS)