Aims: To determine the effectiveness of 3, 6, and 9 liters of physiological saline for wound irrigation in grade II open fracture at lower extremity in reducing the number of bacterial colonies Study Design: This observational study determined the quantity of physiological saline for wound irrigation in grade II open fracture at lower extremity which is effective in reducing the number of bacterial colonies. Place of Study: Moewardi Hospital Emergency Room and the Microbiology Laboratory of the Faculty of Medicine, Universitas Sebelas Maret. Methodology: 16 patients with grade II open fracture at lower extremity who came and received treatment was included. Patients with grade II long bone open fracture less than six hours, patients with multiple open fractures of the long bones taken only in one place, patients who had not received medical treatment since the incident were included. Patients suffering from previous bone and/or soft tissue infections at the fracture site and suffering from multiple trauma who should receive immediate life-saving measures were included. Results: There were 12 patients who met criteria inclusion. After 3 L irrigation, there was a decrease in the amount of bacterial colony, same as 6 L irrigation, while there was no increase in the number of bacterial colonies in 9 L irrigation. There were significant differences in 3L, 6L, 9L irrigations (p = 0.001), but the most effective irrigation fluid was in 9 liters compared with 6 liters (p <0.05). Conclusion: Wound irrigation with 3, 6, and 9 liters of normal saline will significantly reduce the number of bacteria. However, irrigation with 9 liters of normal saline dilution in grade II open fracture at the lower extremity is the most effective.