Children's bicycles are the product most often involved in leisure accidents to children. One of the possible reasons for this might be a lack of fit between the dimensions of the bicycle and the dimensions of the child. In a project entitled KIMA-1, some 33 dimensions of 279 children (aged 2.5-5.5 years) were measured at seven infant welfare centres in the province of Zuid, Holland. These data were used to compare dimensions of children with dimensions of bicycles. Furthermore, the requirements regarding bicycle dimensions laid down in product safety acts of different countries were compared with both the results of KIMA-1 and some bicycles available in shops. It is concluded that maximum product safety and comfort of the bicycle are achieved when the bicycle is fitted to the dimensions of the child. Enhancement of this fitting process can be achieved by relating the dimensions of the bicycle to the stature rather than to the age of the child. The comparison of the KIMA-1 data to the dimensions laid down in product safety acts led to the conclusion that Dutch children are larger than the population on which the safety dimensions are based. Furthermore, secular changes in body dimensions call for a revision of the relevant safety dimensions in 10-15 years.