Plasma digoxin-like immunoreactive factor (DLIF) has been detected in various pathophysiological conditions associated with volume expansion. In this study, using radioimmunoassay, we confirmed the existence of high levels of DLIF in the stimulated foUicular fluid, a rapidly volume-expanding biological model. The concentration of the various fractions of DLIF in foUicular fluid was 2–9 times higher than in plasma, suggesting local concentration or production. No difference in concentration was observed between follicles containing fertilized oocytes and follicles with unfertilized oocytes. The role of DLIF in follicular homeostasis remains to be further investigated.