Nineteen patients with Type 2 diabetes were treated with glipizide for 2.5-6 months, and measurements made of metabolic variables before and after glipizide treatment. For purposes of analysis, the glipizide associated decrease in fasting plasma glucose concentration was used to divide patients into 'good' responders (decrease of 4.0 mmol l-1 or more, n = 9) or 'fair' responders (decrease of 3.0 mmol l-1 or less, n = 10). Good responders had a significantly greater fall in their mean (+/- SE) hourly plasma glucose (6.3 +/- 0.6 vs 2.7 +/- 0.3 mmol l-1, p less than 0.001) and NEFA (164 +/- 40 vs 60 +/- 37 mumol l-1, p less than 0.05) concentrations from 0800 to 1600 h in response to meals (0800 and 1200 h) than did the fair responders. However, the increase in hourly plasma insulin concentration following glipizide treatment was the same in the good (323 +/- 103 to 413 +/- 124 pmol l-1) and fair (276 +/- 42 to 345 +/- 43 pmol l-1) responders.(ABSTRACT TRUNCATED AT 250 WORDS)