Abstract: We compared analgesic effects of intramuscular pethidine to diclofenac sodium and indometacin suppositories. This study is a semiexperimental clinical trial study over 55 patients of 17 to 60 years old who had undergone unilateral inguinal hernioplasty. These patients divided into 3 groups incidentally the first group including 17 patients who received 100 mg indometacin suppository every 8 h to relief postoperative pain. The second group of 18 patients who received 100 mg Diclofenac Na suppository every 8 h and the third group including 20 patients who received 0.5 mg kg-1 body weight pethidine intramuscularly every 8 h and the first dose of each drug started 2 h after termination of operation. The severity of pain was checked by Visual Analogue Scale (VSA) method every 2 h for 24 h. Mean pain severity checked and compared in 6 h intervals. Mean pain severity and standard deviation in the first 24 h were 23±12 for indometacin and 27±12 for pethidine and 31±9 for diclofenac Na groups respectively. There is no meaningful difference in pain relief during the first post op day. We concluded that Indometacin and diclofenac Na suppositories are good substitutes of intramuscular pethidine to relief post op pain during the first post op day.