The objective of this investigation was to develop a bleomycin depot based on monolithic microparticulate technology to suppress tumour growth and to maintain constant plasma drug concentrations within an optimal therapeutic window over a prolonged period of time. Formulations were optimized with biodegradable poly-epsilon-carpolactone and evaluated in vitro for physicochemical characteristics, drug release in phosphate buffered saline (pH 7.4) and evaluated in vivo in tumour bearing mice. This investigation revealed that upon subcutaneous injection, the biodegradable depot-forming poly-epsilon-carpolactone microspheres controlled drug release and suppressed tumour growth kinetics significantly compared to control. A preliminary pharmacokinetic evaluation exhibited steady plasma drug concentrations during the study period. This formulation with its reduced frequency of administration and better control of drug disposition is expected to provide an economic benefit to the user compared with products currently available for chemotherapy.