The effect of triethyllead (TriEL) on the morphology and motile activity of Walker 256 carcinosarcoma cells was investigated. It was found that both 2 and 5 microM TriEL affected the cellular motility in a dose- and time-dependent manner. Initially, 2 microM TriEL caused the formation of blebs instead of lamellipodia at the front of some cells and stimulated the migration of Walker cells, but after 2 hours of 2 microM TriEL treatment, a reduction of cellular motility was observed. In the presence of 5 microM TriEL, Walker 256 carcinosarcoma cells rounded up, and their rate of movement was reduced. Moreover, the treatment of Walker carcinosarcoma cells with TriEL caused the disruption of microtubules and affected the F-actin distribution at both concentrations. At a concentration of 2 microM TriEL, the actin staining intensity was greatest in the tail of front-tail polarised blebbing cells and the actin layer was very thin at the leading edge. The control cells showed linear cortical F-actin distribution and somewhat less intense cytoplasmic staining at the same TriEL concentration. Cells treated with 5 microM TriEL showed an under-membrane pattern of actin distribution.