Achondroplasia is the most prevalent chondrodysplasia and numerous authors have documented the varied social and medical complications that may compromise a full and productive life. Complications include cervicomedullary compression, spinal stenosis, restrictive and obstructive lung disease, otitis media, and tibial bowing, among others. These known complications have led to recommendations for the anticipatory management of such patients. There are relatively few data on the actual rates and timing of these problems. This paper reports data on the rates and age of occurrence of several of these complications based on a review of recorded chart information of 193 patients ascertained from several well established genetic centres with a known interest in the chondrodysplasias. The length of follow up varied and the rates of occurrence at specific age intervals were used to estimate the cumulative percentage affected for each complication. The report includes information on otitis media, ventilation tubes, hearing loss, tonsillectomy, speech problems, tibial bowing and osteotomy, ventricular shunting, apnoea, cervicomedullary decompression, and neurological signs attributable to spinal stenosis.