Introduction:The use of a mouthwash augments mechanical removal of plaque by brushing and flossing and helps maintain oral health through its antiplaque and antibacterial chemical properties. Aim: to evaluate and compare clinically and microbiologically the effectiveness of chlorhexidine and sodium hexametaphosphate mouth rinses on dental plaque in children. Materials and methods: This randomized clinical trial included 40 normal apparently healthy and cooperative children aged 8 to 10 years and selected from the outpatient dental clinic of Pediatric Dentistry Department, Faculty of Dentistry, Suez Canal University. Children were randomly divided into 2 groups as follows: Group I: included (20) children who rinsed with Chlorhexidine (0.2%) and Group II: included (20) children who rinsed with Sodium Hexametaphosphate (7%). Clinical evaluation was performed by measuring gingival and plaque indices scores at all evaluation periods. Microbiological evaluation was performed by direct examination of bacterial cultures. Results: Sodium hexametaphosphate 7% mouth rinse showed a superior effect compared to chlorhexidine 0.2% mouth rinse in terms of improvement in the clinical scores and decreasing the microbial counting. Conclusion: Sodium hexametaphosphate 7% mouth rinse is a promising candidate of mouthwashes.