To increase the high production of 1-deoxynojirimycin (DNJ) from Streptomyces sp. SID9135, the effect of various carbon sources, nitrogen sources, cationic metal ions, the initial pH of the medium, and agitation speed were investigated. The most effective carbon and nitrogen sources were found to be lactose 2.5% (w/v) and soybean meal 2.0% (w/v), respectively. None of the cationic metal ions examined had any detectable stimulating effect on DNJ production except $Fe^{+2}$ ion. The initial optimum pH for DNJ production ranged from 6-8 and agitation speed was most effective at 400 rpm. In the jar fermentor experiments under optimal culture conditions, the accumulation of DNJ reached about $640{mu}g$/ml after 5 days of cultivation and the level remained the same for a further two days.