The production of extracellular collagenase by Sreptomyces candidus 91 was strongly influenced by at least two mecanisms. The growth-rate dependent mecanism and part of nature of nitrogen source were suggested by the results obtained in batch cultures and shift-down experiments. Production of collagenase took place in batch culture during growth at intermediate growth rates and was delayed in media supporting high growth rates. Nitrogen source was interfered with collagenase production. Higher collagenase production was obtained with sodium nitrate as sole nitrogen source in nutritive medium. A partial characterization of the activity indicated that it was due to a single metalloprotease with an apparent molecular mass of 170 kDa.