Studies on two types of coccidiosis E. tenella isolated from diseased chickens and E. kofidi isolated from diseased young quails were carried out. Ten 14 day-old quails of the species Alektor is graeca cypriatis and thirty 10-, 20-and 30 day-old chickens of the White Plymuth breed were used. By cross invasion of sporulated oocysts of both coccidia types the shizogonal development in non-specific host birds was observed. It was established that E. tenella finds suitable conditions for an endogenis development no matter how slight, in the coecum of the non-specific host-the young quails, E. kofoidi, however, does not find similar suitable conditions for its development in the alimentary tract of chickens and passes transit. Under certain definite conditions quails can be a potential reservoir of E. tenella in nature.