We recently showed that arsonoliposomes (novel arsenic containg liposomes) demonstrate differential toxicity towards various types of cancer and normal cells, in cell culture studies, as well as anti-parasitic activity. In this study, the in-vivo distribution of the active moiety of these vesicles, As, is evaluated. Sonicated arsonoliposomes were prepared using the arsonolipid with palmitic acid acyl chain (C16) mixed with egg-phosphatidyl choline (PC) and cholesterol (Chol) [C16/PC/Chol at 8:12:10 mol/mol/mol]. A dose of arsonoliposomes, corresponding to 5 mg arsenate/kg was administered by intraperitoneal injection in balb-c mice. At various time points post-injection the mice were sacrificed and the distribution of As in the organs was measured, by atomic absorption spectroscopy. Results demonstrate that a high portion of the dose administered is rapidly excreted; since 1-h post-injection only about 30% of the dose administered was detected cumulatively in the animal tissues. After this the elimination of arsenic was a slow process with a total body elimination rate constant of 0.023 h(-1), corresponding to a half-life of 30 h. Tissues with the highest arsenic concentration during the study period are: spleen-kidneys-stomach, followed by lung, liver, intestines-heart, carcass+skin and finally blood. No acute toxicity, or effect on the body or organ weight of the mice was observed.