Pregnant rhesus monkeys were studied between 109 and 149 days of gestation. Food withdrawal for 48 hours (with free access to water) was accompanied by a decrease in maternal whole blood glucose concentration and an increased maternal arterial plasma 13,14-dihydro-15-keto-prostaglandin F2 alpha concentration. On successive nights of the 48-hour period of food withdrawal, there was an increase in the frequency of myometrial contractions as recorded by uterine electromyogram. In the period after food was returned, blood glucose, arterial 13,14-dihydro-15-keto-prostaglandin F2 alpha concentration, and contraction frequency returned to baseline. Because food withdrawal results in the appearance of the nocturnal contraction pattern seen at term, we suggest that this experimental paradigm may be used as a model for preterm labor.