History and Objectives: Detection of intestinal parasitic infection is usually performed with multiple fecal specimen examination. The present study will show a relationship between the number of samples studied and the detection of intestinal parasitic infection among patients complaining from indegestion.

Materials and Methods: A analytical study was conducted on 150 patients, 72 men (48%) and 78 women (52%), who were referred to the internal medicine clinic of Shaheed Beheshti hospital during the first half of 1996. Three fecal samples were taken in triplicates every other three days and examined for parasitic agents by formalin-ether method at the Central Diagnostic Laboratory of the University. The results of three samples and three different days of sampling were analyzed by the statistical relativity test.

Results: The prevalence of parasitic infection from the first sample collection was 43.3% (65 patients), after the second sample examination, 56.7% (85 patients) and with the third sample 65.3% (98 patients). The prevalence of infection for the first, second and third day was 43.3%, 23.5% and 20% respectively.

Conclusion: The number of fecal samples studies has significant effect on the detection of intestinal infection. However, the prevalence rates were lower compared to previous studies. Therefore, it is recommended that a similar study on healthy individuals may be conducted.