Decreased muscle strength with aging is associated with functional disability in older adults. However, few studies have longitudinally evaluated the rate of muscle strength loss and the risk factors for the loss in older men. This study examined the patterns and determinants of muscle strength change with aging in a healthy older male population. The study participants were 321 men (age range 51-84 yrs) recruited from population-based listings in the Pittsburgh region, USA. Grip strength was measured at baseline and after an average of 7-years of follow-up. The amount of longitudinal rate of grip strength loss was 2.8% per year (a total of 20% decline during 7-year follow-up). Although all age groups experienced a decline in strength during follow-up, the rate of loss accelerated with age. After adjusting for baseline measurement, grip strength loss ranged from 2.0% decline per year for men aged < 60 years to 3.4% decline per year for men aged 70 years or older (p < .0001). Multivariate analyses revealed that besides older age, other risk factors also contributed to the loss of muscle strength in older men, including back pain, use of calcium channel blockers, caffeine intake, and height and weight loss.