Purpose: This retrospective study assessed the effectiveness of submucosal (SM) midazolam (M), oral chloral hydrate (CH), hydroxyzine (H), and nitrous oxide (N) 99 uncooperative pediatric dental patients over 182 sedation sessions. Methods: Selection criteria included good medical health (ASA I), from 2 to 6 years of age, uncooperative behavior, and the need for restorations and dental surgery. The children who was administerated with CH H, N was Group 1 (48 case). The children who was administerated with CH, H, N, M was Group 2 (51 case). All the patients received oral CH (50-70 mg/Kg), H (1 mg/Kg) and N (less than 50%). Additionally the Group 2 received SM midazolam (0.1-0.2 mg/kg). Behavior response was rated as quiet (Q), crying (C), movement (M), or struggling (S) every 5 minutes through operative procedures. Behavior response rating was assigned to Houpt scale of Overall behavior. Data was analyzed using Chi-Square Test. Results: The Group 2 had more effective (88.2%) than the Group 1 (68.8%)(P = 0.05). Also, vomiting response decreased in the Group 2 (94.4%) than those with oral administration of chloral hydrate alone without SM midazolam (77.1%)(P = 0.05). Conclusions: SM midazolam improved the quality of sedation and vomiting response.