The morphological development and growth characteristics of the actinomycete Streptomyces natalensis were studied in submerged culture. The morphology of the organism was monitored using semi-automated image analysis. A protocol was developed for taking geometric measurements of the cell population in terms of pellet area, perimeter and diameter. The organism was found to be pH sensitive and, under certain circumstances, was shown to suffer from oxygen limitation. The optimum inoculum for a 100 ml, fermentation (in a 250 mL shake flask) was found to be a 5 mL aliquot o f a 96 hour old culture. However, a 100 mL culture was employed, despite superior performance at the 50 mL scale, due to reproducibility problems encountered with the smaller volume. When S. natalensis was cultivated in a 150 mL culture (in a 250 mL flask) the organism was found to be subject to oxygen limitation. Medium composition also affected the growth of the organism, with a YEPD-based medium and an actinomycete medium developed by Sarra et al. (1996) resulting in the greatest levels of biomass production. With the exception of C aC 03, concentrations of the individual components in a medium developed by Struyk and Waisvisz (1975) were found to be optimal, although yielding lower levels o f biomass than the YEPD or Actinomycete media. If the calcium carbonate concentration was reduced from the recommmended 8 g/L to 4 g/L, biomass production was enhanced. The organism grows predominantly in a pelleted form with some filamentous clumps present under certain conditions. The pellets increase in size until the culture is approximately 73 hours old, at which time the pellets undergo some form of disintegration which may be caused by lysis or breakage due to pellet-pellet collisions. After this time, the average pellet area decreases sharply to a stable value. This pattern is relatively insensitive to changes in media components or concentrations. The only exceptions are during cultivation in either YEPD or actinomycete media (Sarra et al., 1996), where the percentage of filamentous clumps present in the sample increases consistently.