['To determine the actual need for orthodontic treatment in the late mixed dentition according to the German KIG system (Kieferorthopädische Indikationsgruppen = Orthodontic Indication Groups). By comparing the findings with those of the early mixed dentition, we aimed to evaluate whether a change in the spectrum of malocclusions would occur.', 'Dental check-ups took place in schools in Frankfurt am Main, during which the orthodontically-relevant symptoms of 1251 schoolchildren (female 49.5%, male 50.5%) in grades 4 and 5 were recorded and compared with findings documented 4 years earlier in the same classes at the same schools.', 'Of those orthodontic malocclusions in need of therapy and covered by the statutory health insurance, lateral crossbite and enlarged overjet (more than 6 mm) dominated by 9.2% and 8.7%, respectively, among the 9- to 11-year-old children. Of all the malocclusions recorded within the KIG-group showing a treatment need degree > or = 3, category D4 (overjet greater than 6 mm) at 17.4% was the most frequent, followed by K4 (unilateral crossbite) at 15.3%, and M4 (negative overjet up to -3 mm) at 14.9%. 41.4% of all the children examined presented a treatment indication according to statutory health insurance directives (KIG > or = 3). The 10% reduction in treatment cases financed by statutory health insurance has been achieved in any case [1], as mandated by health policy.'] Do prevalence and development of KIG-relevant symptoms in primary school students from Frankfurt am Main?