Various plant oils (50 g l(-1)) increased the production of erythromycin by Saccharopolyspora erythraea. Maximum titer of erythromycin in media containing black cherry kernel, walnut, rapeseed, olive and cottonseed oils and control medium were 3.5, 2.8, 2.6, 2.1, 1.9, 0.7 g l(-1), respectively. Erythromycin production media containing rapeseed or cottonseed oil was growth-dependent but not in other media used.