Two dosage forms of etoposide diluted by saline solution (Etp-sol) and etoposide particles suspended in oil (Etp-oil) were examined for the toxicity and therapeutic effects when injected intraperitoneally (ip) in mice. The 50% lethal dose (LD50) values for two weeks observation were 135 mg/kg in Etp-oil and 108 mg/kg in Etp-sol. Two days after intraperitoneal transplantation of 10(6) cells/mouse of P388 leukemia to CDF1 male mice, etoposide was injected intraperitoneally in the form of Etp-oil or Etp-sol. In the mice receiving 20mg/kg of etoposide, 11 of 19 mice given Etp-oil and 3 of 20 given Etp-sol survived to day 60. In the mice receiving 80 mg/kg of etoposide, 1 in 20 treated with Etp-oil and 8 of 20 treated with Etp-sol died from by the toxicity.