Previous work has shown that radioactive colloids can cure Ehrlich ascites tumor. In this experiment, the dose of colloidal 198Au needed has been correlated with the number of tumor cells inoculated. On Day 1, varying numbers of Ehrlich cells (10(2), 10(3), 10(4), 10(5), 10(6)) were injected intraperitoneally into 310 BALB/c male mice. Two hours later, varying doses (10, 20, 40, 80, and 160 muCi) of 198Au were injected intraperitoneally. Controls were injected with normal saline. Generally, the lower cell inoculums and higher doses of 198Au yielded better survival rates.