The present experiment was carried out to investigate arsenic levels in blood, liver, kidney, muscle, lung and heart tissues in mice orally administered arsenic trioxide (As₂O₃) and sodium arsenate (Na₂HasO₄). The animals were divided into one control and two experimental groups. Arsenic trioxide and sodium arsenate were given in the daily doses of 5 mg As/kg orally with water to experimental groups. During the administrations, in 10, 20, 40, 60 and 90^th days, 6 animals were slaughtered. Arsenic levels in blood and tissue samples were determined spectrophotometrically by silver diethyldithiocarbamate procedure at 540 nm.

It was observed that the highest mean levels of arsenic determined in liver and kidney of animals treated with arsenic trioxide at 3.49 µg/g and 3.16 µg/g respectively. In this group, the mean levels of arsenic in blood, muscle, lung and heart samples were lower than the mean levels of arsenic in liver and kidney. In animals given sodium arsenate, the highest mean levels of arsenic were determined in kidney, blood and liver at 3.38 µg/g, 2.10 µg/ml and 1.88 µg/g respectively. The mean arsenic levels were lower in other tissues. On the other hand, when these groups were compared, the mean arsenic level was higher in liver in the arsenic trioxide given group. However, the mean level of arsenic in kidney in the group treated with sodium arsenate was determined higher than group given arsenic trioxide. The mean level of arsenic in the blood was approximately equal in both groups.

The highest levels of arsenic were observed in liver at 10th and 20th days and at 40, 60 and 90th days in kidney in the group treated with arsenic trioxide. On the other hand, the highest levels of arsenic were determined in kidney at all periods, in the group treated with sodium arsenate

In conclusion, the arsenic levels in liver was observed to increase significantly in the group treated with arsenic trioxide, but the highest arsenic levels were obtained in kidney, in the group treated with sodium arsenate.