The vertical forces acting on the sole of the foot in walking have been measured in 24 diabetic patients with neuropathic ulceration of the foot using a load-sensitive surface divided into 128 load cells, and compared with those in two groups of controls: (a), 21 diabetic patients with peripheral neuropathy but no ulceration and (b) 47 normal individuals. The results showed that the patients with neuropathic ulceration were significantly heavier, that diabetic patients with neuropathy, with or without ulceration, transmitted proportionally less force through the toes than normal individuals, and showed a medial shift of the force transmitted through the metatarsal heads. All plantar ulcers occurred at the site of maximum loading. The absolute force at the site of maximum loading was significantly greater in the patients with ulcers than in both control groups, through there was a considerable overlap. A significant difference remained even when the absolute force had been corrected for differences in toe loading and body weight, indicating that a further factor (or factors) must contribute to the development of these localized areas of high loading.