In a recent study on gait training in young children with disabilities, gait velocity and the Gross Motor Function Measure (GMFM) failed to identify changes in locomotor status that could be discerned by trained observers from video records. This led to the development of a clinical measure that would be sensitive to changes in the period preceding the onset of independent gait. The first part of this paper describes the development of the SWAPS (Supported Walker Ambulation Performance Scale), and the second part presents the results from a preliminary testing of its psychometric properties. Three experts were asked to determine the criteria they would use to determine changes in the walking performance of nine children with spastic cerebral palsy. After examining two series of video records taken at four-month intervals, the SWAPS was proposed. It consists of four dimensions: A) support, B) posture, C) quality of steps, and D) quantity of steps. These four dimensions are weighted so that support is worth 40% and the other three dimensions 20% each of the total score (100%). Each dimension is scored on a four-point Likert scale. The interrater reliability of the SWAPS was studied by having four physiotherapists score video records of the walking performance of the nine children. The intraclass correlation coefficient calculated for the total SWAPS score was 0.95, indicating a high-interrater reproducibility. Construct validity was also studied by correlating the SWAPS scores to the Gross Motor Function Measure (GMFM). A Spearmanpof 0.68 computed between the SWAPS and GMFM scores indicates a good relationship between the performance measured by the two scales. There are limitations to the present study: the development of the scale was made a posteriori using data recorded before its development in a small convenience sample, and the same sample of subjects was used for both the development and the testing of the scale. Despite these limitations, the present results are encouraging, and valuable information can be drawn from this preliminary study. Suggestions to improve the scale in future investigations are discussed.