Atlantic Bonito and horse mackerel were investigated for proximate and elemental composition throughout the year. Two fish species were collected from the Istanbul local fish market from December (2006) to November (2007) during the fishing season. Highest protein values were found in the June for Atlantic Bonito, in July for horse mackerel. Highest fat value of Atlantic Bonito and horse mackerel were determined in November. Trace and potential toxic minerals (mercury, cadmium, lead, copper and zinc) exceeded the legislative limits in some months of the year. The highest concentration among the elements was obtained for sodium, potassium, calcium, magnesium, manganese, iron, zinc, iodine and selenium throughout the year.