Background: Colorectal cancer (CRC) is the third most prevalent and the third leading cause of cancer-related deaths in Iran. Our aim was to investigate five mononucleotide statuses among Iranian patients with sporadic colorectal cancer.Materials and Methods: In this experimental study 80 sporadic CRC patients were evaluated for MICROSATELLITE instability (MSI). The pentaplex panel including 5 quasi mononucleotide MICROSATELLITE MARKERS (NR-21, BAT-26, BAT-25, NR-27 and NR-24) was used. The MSI analysis was performed on paired tumoral DNA from cancerous tissues and genomic DNA from whole blood. MSI carriers were identified by analysis of tumor tissue using polymerase chain reaction.Results: Our findings showed that MICROSATELLITE instability was detected in 36 of 80 cases (45%) with colorectal cancer. MSI analysis revealed that 17 cases of MSI-H (21%), 19 MSI-L (23%) and 44 MICROSATELLITE stable tumors (55%). Instability is observed in the tumoral DNA compared to the DNA from the normal DNA sample. The most instable MARKERS were NR-21, NR-24 in which instability was detected in 45% of patients.Conclusion: Using a panel including 3 mentioned MSI MARKERS should be more promising MARKERS for identifying MSI status in patients with sporadic colorectal cancer.