During a period of 8 months 121 male and 99 female joggers were interviewed by a standardised questionnaire in respect of their running behaviour and problems caused by jogging. Only such runners were included who had jogged regularly on at least 2 days, regarding women on at least one day per week for at least 30 minutes during the last 2 years. Additionally a detailed orthopaedic examination was carried out in the ambulance of the Orthopaedic University clinic. The overwhelming majority of male and female joggers had a secondary education and practised easy physical activities. Only 4 per cent of the interviewed persons worked physically hard. In connection with jogging, 67 male and 44 female joggers developed signs at the locomotor system. Among the major problems with regard to running were Achilles tendinitis, calf muscle strain, shin splints and complaints referring to foot deformities. Injuries were seen only rarely. Jogging on forest grounds and cinder paths is less strenuous compared to asphalt tracks or tartan paths. Training errors were among the main causes of complaints occurring during running. Traumatic or posttraumatic influences as well as incorrect footwear were of secondary importance regarding the occurrence of complaints.