Vascular smooth muscle cells (SMCs) play a key role in the development of major arteries. Furthermore, abnormal growth of vascular smooth muscle cells has been implicated in the progression of major diseases of the cardiovascular system. Here, we report detection in primary cultures of bovine vascular smooth muscle cells of mRNA for two growth-state-related genes, 2F1 and 2A9, which code for a mitochondrial ADP/ATP carrier and calcyclin, respectively, and on the characterization of their cell cycle expression. Cultures of exponentially growing smooth muscle cells were made quiescent by serum deprivation. Upon readdition of serum, cells entered the cell cycle synchronously; DNA synthesis began 12 h post-serum addition. Levels of 2F1 and 2A9 RNA were low in quiescent cells and increased between 2 and 4 h post-serum addition. No changes in the rates of transcription of the 2F1 or 2A9 genes were detected by nuclear run-off assays during the time course. Thus the regulation of changes in expression of 2F1 and 2A9 in early G1 is mediated post-transcriptionally.