Aortic cells were isolated from 9- and 12-day embryonic chick aortas and cultured for varying periods after first passage. Cells obtained from 9-day tissue remained indefinitely as monolayers and possessed a relatively low rate of tropoelastin synthesis. Cells obtained from 12-day tissue remained monolayers for 4 to 8 days, after which time portions of the culture contracted into matrix containing chemically definable insoluble elastin and forming desmosine cross-links. The rate of tropoelastin synthesis was significantly higher in the 12-day derived cells suggesting that these cells had been committed to elastogenesis in vivo and retained this commitment in vitro. A chick tropoelastin cDNA was obtained and partially characterized from a lambda gt11 expression cDNA library. Using the tropoelastin cDNA probe, measurement of the steady-state level of tropoelastin revealed that the increased rate of tropoelastin synthesis in the 12-day cells was accompanied by a significant increase in the level of tropoelastin mRNA steady-state levels. The aortic cell cultures present an important model system for extending studies of chick aortic elastogenesis. The aortic cell cultures synthesize tropoelastin at a rate 10% less than the corresponding organ culture. Significantly, the production of tropoelastin is productive in formation of insoluble, chemically definable elastin. The definition of insoluble includes both amino acid composition and desmosine formation.