Height and muscle strength have reportedly changed among Japanese youth during the past 10 years. Height has increased, and the back muscles have become weaker than 10 years ago. We compared the lumbar lordosis of youth today (113 men and 76 women) and of 10 years ago (85 men and 62 women). Lumbar lordosis and sacral inclination were measured on lateral standing radiographs of the lumbar spine. We also measured the same parameters among adults today (63 men and 63 women) and 10 years ago (56 men and 73 women) to study postural changes in another generation. In both men and women, the lumbar lordosis and the sacral inclination of youth today were approximately 10 degrees larger than they were 10 years ago ( P < 0.0001). However, there was no significant difference between the values among adults today and those of the same generation 10 years ago.