Abstract: The present invention provides a sustained release microsphere composition comprising- (i)microspheres comprising(A)a biodegradable polymer which is a homopolymer of lactic acid or a copolymer of lactic acid glycolic acid having a monomer of goserelin or range of about 1:1 to about 3:1 and(B)a therapeutically effective amount of goserelin or a pharmaceutically acceptable salt thereof, and (ii)pharmaceutically acceptable excipients, which when injected intramuscularly, delivers goserelin or a pharmaceutically acceptable salt thereof, for a period of at least one month.