Studies on the dynamic biochemical and morphological events occurring during steroidogenesis in granulosa cells suggest that the organization and expression of the actin-cytoskeleton may play a major role in the transduction of endocrine and paracrine steroidogenic signals, and in the coordination between the organelles involved in this process. Since steroid hormones are not stored intracellularly, regulation of their production is dependent mainly on the expression of genes coding for membrane-bound steroidogenic enzymes. Recently, the expression of oncogenes of the ras family was also implicated in the regulation of steroidogenesis.