The tumor growth delay produced by the combination of etoposide with the alkylating agent CDDP or BCNU and Fluosol-DA with carbogen breathing in three model tumor systems was examined. The addition of Fluosol-DA to etoposide treatment increased tumor growth delay 2.8-fold, 3.3-fold and 2.2-fold in the FSaIIC fibrosarcoma, the Lewis lung carcinoma and the SW2 small-cell xenograft, respectively. In both the FSaIIC fibrosarcoma and the Lewis lung carcinoma the combination of etoposide treatment with CDDP produced an additive effect. When Fluosol-DA was added to this combination the tumor growth delay increased 1.9-fold and 1.4-fold in the FSaIIC fibrosarcoma and the Lewis lung carcinoma, respectively. Adding Fluosol-DA to a treatment regimen with etoposide and BCNU produced a 2.2-fold, 2.0-fold and 1.6-fold increase in the tumor growth delay of the FSaIIC fibrosarcoma, the Lewis lung carcinoma and the SW2 small-cell xenograft, respectively. The effect of these various treatment combinations on tumor cell survival was assessed in the FSaIIC fibrosarcoma. When the alkylating agents CDDP or BCNU were prepared in Fluosol-DA, there was an additional increase in tumor cell kill, so that with CDDP there was 2.1-fold and 4.7-fold increase in tumor cell kill and with BCNU there was 1.5-fold and 1.2-fold increase in tumor cell kill compared to the drug plus Fluosol-DA and the drug plus Fluosol-DA/carbogen breathing, respectively. The combination of etoposide and CDDP led to less than additive cell killing, and the combination of etoposide and BCNU appeared to be additive, as predicted by simple product summation, in all of the treatment conditions examined. Both etoposide + CDDP and etoposide + BCNU produced additive or less than additive toxicity to bone marrow as measured by CFU-GM.