Purpose. The aim of the study was to assess lactate and glucose concentrations as indicators of anaerobic capacity in a highlyranked female junior swimmer. Methods. Ten trials of a 5 × 200 m backstroke step test were performed between December 2008 and July 2011. Each trial was video-recorded and blood samples were drawn from the ear lobe 1 min after completion of each step to measure lactate and glucose concentrations. Results. During maximal effort, lactate concentrations of 5.1 to 13.1 mmol · l-1 were recorded, while glucose concentration varied from 6.6 to 8.1 mmol · l-1. Correlations between lactate and glucose concentrations were significant in most tests. The shape of lactate and glucose curves revealed an improvement in the swimmer’s endurance ability during subsequent tests. Conclusions. Analysis of fluctuations in lactate and glucose concentrations appears to be a relevant indicator of the anaerobic capacity of experienced swimmers.