To detect the intradaily variation of the lower leg length in 14 children, the right lower leg length was determined using a non-invasive lower leg length measuring device at 3 set times of each day during a period of 3 wk. The mean standard error of the determinations was 0.04 mm. For the whole group, the lower leg length decreased significantly during the time interval from 08:00-12:00 h. (Friedman''s related samples test, P < 0.01). The decrement amounted to 0.6 mm. During the rest of the day, the changes in the lower leg length were not significant. A consistent decrement of the lower leg length during the day in combination with a total growth of 1.08 mm during the 3 wk period suggested that growth in length of the human lower leg occurs during the night.