Within a prospective study of back function and pain before and after basic military training, the leg length inequality (LLI) was assessed, in steps of less than 0.5 cm. (equal), 0.5-1.5 cm, 1.6-2.5 cm, 2.6-3.5 cm and more than 3.5 cm. Around six hundred young men were examined three times over a period of four years. LLI of 0.5-1.5 cm was found in 32%, and 4% had a difference of over 1.5 cm. Pelvic rotation was noted in 15% of the cases. The average total agreement of identifying LLI was 64% between the three examinations. No correlation was found between LLI and back-pain or pain-provocing tests. In those with LLI in standing there was a tendency towards more remarks on SI-joint mobility tested in lying. During the follow-up period, no correlation of the LLI and the result of the other examination variables could be found.