SUMMARYCryptosporidial infection was diagnosed in a flock of 4-week-old common quails (Corturnix cortunix). The main gross pathological changes were excess mucus in the trachea, nasal mucosal congestion and shrunken bursa of Fabricius (Bursa cloacalis). Microscopically, the main changes were epithelial deciliation and hyperplasia and inflammatory cell infiltration of the lamina propria in the trachea, bronchi and nasal cavity; epithelial hyperplasia in some oesophageal and salivary glands, and epithelial hyperplasia and follicular atrophy in the bursa. Protozoan parasites attached to the affected epithelium were identified by electron microscopy as Cryptosporidium spp. INTRODUCTIONCryptosporidium species (of suborder Eimeriorina and family Cryptosporidiidae) are coccidian parasites associated with the microvillus border of the host epithelial cells. These parasites are known to infect reptiles (Anderson et al, 1968;Brownstein et al.,