Objectives The decline in the growth hormoneinsulin-like growth factor-I (GHIGF-I) axis during normal aging might be involved in the changes in body composition associated with increasing age. We conducted a study to investigate serum IGF-I levels across different age categories and a possible association between serum IGF-I and measurements of body composition in older people. Design A cross-sectional analysis of community dwelling older people, which participated in a large longitudinal cohort study (Longitudinal Aging Study Amsterdam). Subjects 1319 subjects, 644 men, mean age 75·6 ± 6·6 years and 675 women, mean age 75·4 ± 6·6 years. Main Outcome Measurements IGF-I, body mass index (BMI), waist, waist-hip ratio (WHR), fat mass, lean body mass and total bone mineral density. Results IGF-I levels were significantly lower in the highest age categories. BMI and biceps skinfold measurements were lower in the lowest IGF-I quartile in men aged ≥75·5 years. In men with a low total physical activity score (<131 minday), BMI, WHR and skinfolds were significantly lower in the lowest IGF-I quartile. In women with a high total physical activity score (>174 minday), WHR was lower in the lowest IGF-I quartiles. Conclusion In this large cohort of community dwelling older people, we observed lower serum IGF-I levels in the higher age categories. A low serum IGF-I was associated with significantly lower measurements of body composition, such as BMI, skinfolds and WHR. These results do not support previous findings that high IGF-I levels are favourable for a healthy body composition in community dwelling older people. © 2010 Blackwell Publishing Ltd.