To test the effect of chronic starvation on gonadotrophin secretion and oestrous cycles, rats were fed 50% of their normal chow consumption for 16 days. This caused an increasing rate of anoestrus which became significant during the third expected cycle (6 of 10 rats, P less than 0.02) and increased to 8 of 10 rats (P less than 0.0001) between day 12 and 16. The accompanying weight loss was around 13 and 17%, respectively. Pituitary weights in intact rats killed on dioestrus became significantly different after 8 days of chow reduction (12.8 +/- 0.2 vs 11.3 +/- 0.4 mg, P less than 0.02) with further reductions in groups killed after 12 and 16 days. At this time dioestrous serum FSH levels were significantly increased in starved rats (112 +/- 16 vs 161 +/- 13 ng/ml, P less than 0.01), while serum LH levels decreased significantly after 12 days (25.0 +/- 3.4 vs 13.1 +/- 8.8 ng/ml, P less than 0.001). Starvation decreased the LH response to LRH administration compared to pro-oestrous controls (1934 +/- 672 vs 289 +/- 39 ng/ml, P less than 0.05), whereas the FSH response was not impaired (457 +/- 91 vs 336 +/- 54 ng/ml, P greater than 0.05). In contrast to this pituitary content of LH was similar in both groups, while FSH content was significantly higher in starved animals (13.6 +/- 1.7 vs 19.8 +/- 1.2 micrograms, P less than 0.01). Chronic starvation immediately after ovariectomy did not affect the post-castrational rise of gonadotrophins. However, LRH administration caused higher serum FSH levels in starved rats (1540 +/- 91 vs 1833 +/- 90 ng/ml, P less than 0.05), whereas LH values did not differ (908 +/- 192 vs 721 +/- 153 ng/ml, P greater than 0.05). Gonadotrophin content per pituitary in castrated rats after 16 days of starvation was unchanged.