Cryptosporidium, an enteric coccidian, is a common enteropathogen in birds and mammals including human particularly in immunocompromised individual. In this survey rectal swabs from 191 dogs that referred to Small Animal Teaching Hospital of Veterinary Faculty in Tehran (101 household & 90 stray dogs) and from 100 household dogs that referred to Small Animal Teaching Hospital of Veterinary Faculty in Isfahan and from 150 dogs that referred to Dr. Kalantari Small Animal Hospital in Sari (120 household & 30 stray dogs) were collected from three aged groups (0-6 months, 6 months to 4 years and over 4 years). The samples were collected From May 2003 to November 2004.

Two smears were prepared from each swab sample. One smears underwent Fluorescent Auramine and the other Modified Ziehl-Neelsen technique.

Oocysts were detected by both staining methods in one male household dog with clinical signs of diarrhea (aged 4 months) and in one male stray dog without diarrhea (aged 8 months). There was no significant difference between the household and the stray dogs in Tehran. Oocysts were not detected in any dog in Isfahan and Sari.

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