This article describes a retrospective inventory of various categories of complications which occurred in a sample consecutively treated patients with Class II division 1 malocclusion.Retrospective, descriptive study.Treatment was performed with a headgear-activator and a edgewise appliance. All patients originate from one orthodontic specialist office and were between 10 and 14 years of age during treatment. From the group of 600 patients 100 (n = 100) were randomly selected for the study. A standard form was used for the inventory of the complications. The complications were divided into 5 categories: dental, skeletal, functional, psychosocial and multiple (two or more complications).In the group of 100 patients no complications were found in 48 patients (48%); 52 patients showed complications (52%). From these 52 patients 29 showed one complication, 19 had 2 complications, 4 showed 3 complications. In total 79 complications occurred divided as follows: dental complications 23 (29.1%); skeletal complications 19 (24.1%); functional complications 15 (19.0%); psychosocial complications 22 (27.8%).Complications occur very frequently in the treatment of Angle Class II division 1 malocclusions. These complications may occur in various combinations and may compromise the treatment result in a variable way.