Thirty mature Debouillet ewes were used to examine effects of exogenous glucose on endocrine, ovarian, and reproductive responses. Treatments were administered from d 5 through 15 of a normal estrous cycle (d 0 = estrus). Fifteen ewes received daily i.p. injections containing 100 mL of saline (.9%, control), and 15 ewes received daily i.p. injections containing 50 g of glucose (100 mL of 50% dextrose). Ovaries were removed from five ewes per group on d 15, and luteal mRNA encoding steroidogenic enzymes and follicular fluid progesterone (P4) were determined. Serum glucose in treated ewes increased rapidly after injection and remained elevated (P < .01) for 4 h after treatment on d 10 and 14 compared with control values. Serum insulin concentration was also greater (P < .01) after glucose treatment on d 10 and 14, but serum growth hormone concentration was similar (P > .10) in both groups on these days. Serum LH concentration and pulsatility were not altered by glucose injection (P > .15). Serum P4 remained elevated longer (P < .05) during the estrous cycle in treated than in control ewes. Corpora lutea from treated ewes also had more (P < .10) mRNA encoding for cytochrome P450 side-chain cleavage enzyme, but mRNA for 3 beta-hydroxysteriod dehydrogenase/delta 5- delta 4 isomerase and follicular fluid P4 were similar (P > .40) between groups. Glucose-treated ewes conceived later (P < .10) and produced fewer lambs (P < .10) than did controls. These data indicate that exogenous glucose and(or) the subsequent increased serum insulin resulted in ovarian changes associated with elevated luteal P4 production.