Oocysts of coccidia of the genes Cryptosporidium were detected for the first time in the faeces of naturally infected calves using centrifugation floatation method with saturated solution of ZnSo4 and Breza's floatation solution. Since the detection of oocysts in the faeces is very difficult, a new method has been prepared. The oocysts recovered from the faeces were sporulated, spherical or slightly elliptical, with a smooth, colourless and thin wall. In the fresh preparation after floatation the oocysts measured 5.4 X 4.6 micrometer on the average, whereas in the smears stained after Giemsa, their average size was 4.8 X 4.3 micrometer. A typical feature of the oocysts is a residual body appearing as a dark point at one pole of the oocyst when observed by optical microscope. The oocyst contains four sporozoites forming a C-shaped rim around the residual body. No sporocysts were recorded. The residual body stains blue and the nucleus dark red by Giemsa's method.