Black sea bream, (Sparus macrocephalus), is a protandrous hermaphrodite. Raised from larvae to 2 years old, the fish were all males but at 3 years old, some sex reversals to females occurred. Attempts were made to induce sex reversal one year earlier than normal by hormone administration and manipulation of environmental factors. 18-month old and 2.5-year old fish treated by oral administration of diethylstilbestrol, combined with lighting, showed good results. After six months, 43% and 66% of the fish changed into female respectively. The control group of 2 year old were all males. Only 12.5% of the 3 year old group changed into females.