The present study was conducted to detect prevalence and risk factors for retrovirus infection of infected cats in a cat population in Iran, by evaluation of 238 client-owned cats of different ages that were tested for the presence of FIV antibodies. The cats were selected from those referring to Veterinary Hospital of Ahvaz University, southwestern Iran from December 2007 to June 2010. Classification was made by age, sex, breed, region and season. The studied cats were divided into two age groups (≤ 3 years and >3 years) and based on clinical signs into two groups. Prevalence of FIV antibodies in these cats was 10.5 % by immunochromatography assay, indicating that this virus is present in the environment. The infection had more prevalence in cats above 3 years (13.9 %) compared with cats less than 3 years (4.6 %). Statistical analysis showed significant difference between different age groups. Mean age of FIV-infected and FIV-negative cats were 4.93 ± 0.43 years (range 1.75 – 10 years) and 4.15 ± 0.20 years (range 0.4 – 15 years), respectively. Prevalence of infection was 12.6% in males and 8.1 % in females; nevertheless the infection was not significant between different sexes (P > 0.05). Six out of 36 cases (16.7 %) which had clinical signs and 19 out of 202 cases (9.4 %) which did not have clinical signs were seropositive, without significant difference between two groups (95 % CI for OR = 1.92). Risk factors for FIV infection were older age (95 % CI for OR = 3.35), access to outdoor (95 % CI for OR = 140.9) and aggressive behavior (95 % CI for OR = 82.71).