Enprostil, a dehydro-prostaglandin E2 analogue, has been tested as treatment for peptic ulcer. Its effect on blood glucose and lipid metabolism in Type 2 diabetes was assessed in a randomized, double-blind trial. Fifteen patients on sulphonylurea therapy received, in addition, enprostil 35 micrograms or placebo thrice daily for two weeks, with a 2-week wash-out before crossover. Data from 12 patients were analysed. After a 530 Cal test breakfast at the end of active treatment, plasma glucose rose from a fasting concentration similar to that after the last placebo dose (10.5 +/- 0.8 (+/- SE) and 10.6 +/- 1.1 mmol l-1 respectively) to 1, 2 and 3 h concentrations which were 1.5 to 2.1 mmol l-1 lower than on placebo (2 h concentration 14.6 +/- 0.9 vs 16.4 +/- 1.3 mmol l-1, p less than 0.05). Serum fructosamine concentrations at the end of active treatment and placebo were 3.66 +/- 0.22 and 3.78 +/- 0.24 respectively (p = 0.051). No changes in fasting or post-prandial insulin concentrations were observed. After 2 weeks of enprostil, fasting serum triglyceride (1.76 +/- 0.18 mmol l-1) and total cholesterol (6.27 +/- 0.29 mmol l-1) concentrations were lower than after placebo (2.14 +/- 0.25 and 7.35 +/- 0.46 mmol l-1, p = 0.031 and p = 0.002, respectively), the latter effect being primarily due to reduced LDL-cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)