At concentrations of 100 micrograms/ml, NIEHS short chrysotile was more cytotoxic than NIEHS intermediate chrysotile (3% and 17% survival, respectively); B(a)P and B(e)P concentrations up to and including 10 micromoles were not cytotoxic. Simultaneous application of NIEHS short chrysotile with B(a)P or B(e)P did not decrease survival synergistically. On the contrary, application of B(a)P simultaneously with NIEHS intermediate chrysotile resulted in increased survival over that of intermediate chrysotile alone (25% and 17% survival, respectively). There were low levels of B(a)P bound to DNA in the presence of NIEHS short chrysotile or NIEHS intermediate chrysotile. Measurable levels of B(a)P-DNA adducts formed both in the absence and in the presence of each size of NIEHS chrysotile. However, there was no strong indication of a perturbation of the level of DNA-B(a)P binding following simultaneous administration of increasing levels of asbestos in addition to 1 micromoles hydrocarbon. The asbestos had no demonstrable influence on the level of B(a)P metabolism during the 24 hr period following simultaneous exposure of asbestos and hydrocarbon.