Iturin, an antifungal lipopeptide, fermentation by Bacillus subtilis was investigated focusing on the effeats of nutrients aeration and specific cell growth rate on iturin production. Cell growth and product formation were not affected by different kinds of carbon sources such as sucrose, glucose and fructose. Soytone concentration above 20g/$ell$ did not influence iturin production. Diauxic growth pattern appeared when only soytone was used as a sole nitrogen source probably due to the shortage of amino acids and/or peptides in soytone which could be favorably assimilated by the cells. The composition of three major components in iturin was not changed significantly by the variation of dissolved oxygen concentration of the culture broth but changed substantially by the change of specific growth rate of the cells.