Ascending and descending stairs is a frequent activity in every-day living. Available data usually describe the ascent and descent pattern of young healthy adults, or elderly people.In order to assess the problems of peadiatric patients during stair ascent and descent, and to evaluate how treatment changes this pattern, a normative data base is needed. This data is lacking in the literature. Therefore, the aim of this study was to collect the kinematic data of healthy children, adolescents and young adults during stair locomotion and to assess the changes in range of movement in hip and knee joints in the sagittal plane. Twenty-seven healthy subjects, aged 6 to 21 years old, participated in the study. The subjects were climbing stairs with dimensions comparable to steps in public building.The data were collected using optoelectronic motion system VICON 460. Helen Hayes marker set and Plug-In-Gait model were used. The data were further processed using Polygon and Matlab softwares. The subjects were divided into 6 subgroups, according to their body stature.Hip and knee kinematics in sagittal plane during stair ascent and descent are reported for all 6 subgroups.The main factor determining the dynamic range of movement in the hip and knee joints during stair locomotion is the body stature / step height ratio. The present paper presents detailed data, which could be used as reference data for assessment of stair locomotion of paediatric patients.