Seven long-running telemedicine networks were surveyed. The networks provided humanitarian services (clinical and educational) in developing countries, and had been in operation for periods of 5-15 years. The number of experts serving each network ranged from 15 to 513. The smallest network had a total of 10 requesters and the largest one had more than 500 requesters. The networks operated in nearly 60 countries. The seven networks managed a total of 1857 cases in 2011, i.e. an average of 265 cases per year per network. There was a significant growth in total activity, amounting to 100.3 cases per year during the 15 year study period. In 2011, network activity was 50-700 teleconsultations per network. There were clear differences in the patterns of activity, with some networks managing an increasing caseload, and others managing a slowly reducing caseload. The seven networks had published a total of 44 papers listed in Medline which summarized the evidence resulting from the delivery of services by telemedicine. There was a dearth of information about clinical and cost-effectiveness. Nevertheless, the services were widely appreciated by referring doctors, considered to be clinically useful, and there were indications that clinical outcomes for telemedicine patients were often improved. Despite a lack of formal evidence, the present study suggests that telemedicine can provide clinically useful services in developing countries.