The aim of this study was to analyse anchorage loss with reduced, in comparison with total mandibular cast splints during Herbst treatment. Lateral head films of 32 Class II division 1 patients (15 females, 17 males) aged 13.0 years with reduced mandibular cast splints (RMS: second premolar to second premolar) and of 34 Class II division 1 patients (19 females, 15 males) aged 13.9 years with total mandibular cast splints (TMS: molar to molar) were analysed before (T1) and directly after (T2) Herbst treatment. Anchorage loss was assessed considering mandibular incisor proclination, changes of lower incisor edge position, and changes of occlusal plane inclination. To assess possible group differences, Student's t-tests were applied. The lower incisors proclined more in the RMS (11.8 degrees) than in the TMS (9.3 degrees) group. However, the amount of incisal edge advancement was less in the RMS (2.9 mm) than in the TMS (3.7 mm) group. The occlusal plane tilted insignificantly less in the RMS (5.7 degrees) than in the TMS (6.3 degrees) group. Reduced and total mandibular casted splint anchorage seemed to be similarly effective. Anchorage loss, measured by mandibular incisor proclination, was greater in the reduced anchorage group, whereas measured by lower incisor edge advancement, it was larger in the total anchorage group. Therefore, RMS can be recommended for Herbst treatment since they are less expensive than total splints.