Using radioimmunoassays, plasma levels of carp gonadotropin (c-GTH) and oestradiol-17 beta (E2) are measured every day in Carp, during induced spawning (water temperature = 15 degrees C). Ten Carps injected twice intraperitonealy with a total extract of Carp hypophysis (0,6 mg/kg BW at Jo and 5,4 mg/kg BW at J1) are compared to a lot receiving only saline solution. No evolution is detected in that last group when in the experimental one E2 level increases with exogenous c-GTH (see table). Even if E2 levels are low at the end of vitellogenesis, steroidogenic structures remain sensitive to an exogenous hypophysial stimulation. Secretion ability differs within individuals (correlation coefficient between total estimated c-GTH and E2 = 0,15).