Insulin-like growth factor-1 (IGF-1) is one of the potential autocrine/paracrine regulators of ovarian function. Not only do relationships exist between follicular fluid concentrations of IGF-1 and various biochemical markers of follicular differentiation, but IGF-1 has also been shown to stimulate both proliferation and steroidogenesis in ovarian cells in vitro (Adashi et al., 1985). The actions of IGF-1 are thought to be modulated by IGF-binding proteins (IGFBPs). Indeed, follicular growth and atresia in the ewe have been reported to be determined more by changes in IGFBPs than by changes in IGF-1 (Monget et al., 1993). However, in mat particular study, stage of follicular development was determined by follicle size and by microscopic examination of the granulosa cells of individual follicles rather than by biochemical markers of follicle status. The objective of the present study was, therefore, to investigate changes in IGF-1 and IGFBPs levels in follicular fluid and to relate these to the physiological status as determined by steroidogenic content of follicular fluid.