The fluctuating asymmetry in Pentaprion longimanus, was estimated by determining the number of rays in pec-toral fins and measurement of four body morphometric characters, i.e. preorbital length, postorbital length, orbital diameter and head length on both sides of the body in 91 individuals from the population of P. longimanus, collected from the waters off Muscat City, The Sea of Oman. Units of ... [Show full abstract] asymmetry were determined as the absolute value of difference between counts on both sides of body. Results indicate that pre and postorbital length and the number of pectoral fin rays demonstrate a higher level of asymmetry than the rest of the characters studied. In the pre and postorbital lengths we also noticed the trend of increase in the asymmetry values with the fish length. The possible cause of the asymmetry in this species was discussed in relation to different pollutants and their presence in the area. The usefulness of the information in future taxonomic studies on P. longimanus was also addressed.