Para-Influenza type 3 virus is one of the most important respiratory system pathogens in cattle and buffalo which causese economical losses in cattle and buffalo raising industries. The aim of this study was to determine the PI3 frequency rate in buffalo calves in Khuzestan tropical area and detect the associated factors. one hundred two serum samples were obtained from buffalo calves in winter, spring and fall seasons of 2004 in Ahvaz city. Virus detection test, serum neutralizing test were performed on the samples. Statistical analysis was performed to show the relationship between disease and season, sex, and age. Among 102 samples fifty (49%) were positive for SN test. In spring 97.1%, in fall 7.5% and in winter 48.1% of cases was positive (p<0.001)a many cases 45% were male and 45.0% were male and 54.8% were female (p=0.441), age of 22.4% of cases were less than 12 months old and all the 12 months old cases were positive (p<0.001). Prevalence of antibody against Para Influenza Type 3 was 49% in buffalo calves in Ahvaz as a tropical area. According to economic losses, administrators' more attentions and further researches are necessary.