Abstract: This study investigated the chloride oregano insecticide sprays such as heptachlor in the four of the most consumed kinds of fishes in the Caspian Sea. This investigation prepared four different kinds of fishes, which arc highly used and available in the Caspian Sea (Sefid, Koli, Kilca and Kafal fish) that we selected 100 samples of fish from the four different hunting region (Chalous and Babolsar city and Khazar Abad and Miankaleh regions) in 2004. After cleaning, we prepared Hun muscle of the samples, then after the process of extraction, we distilled them in vacuum by means of organic solvent and at last we evaluated the remaining and reported based on ppm by Gas Chromatography (GC) with ECD detector. The results of insecticides analyzed in four kinds of fishes and showed that Kafal in the hunting region of Khazar abad had greatest amount of 0.037 ppm. Kilca from Miankaleh had the highest amount of heptachlor, 0.026 ppm (p<0.05) in the case of Sefid and Koli fishes in regions, significant difference was not seen. It is necessary to mention that no research has sofar been done to be a criterion for comparison in this area, But, fortunately the amounts of the insecticide sprays has not reached to standard level in fishes and it raises the alarm health.