Automatic postural responses and effector factors were examined in 10 persons with unexplained falls after clinical examination and 24 older controls. Fallers were more unstable than controls on clinical tests of balance (20% of fallers vs 79.2% of controls were able to stand on one foot (P less than .005), 40% of fallers and 100% of controls were stable while turning in place (P less than .001), postural stress test median score was 12 for fallers and 20 for controls (P less than 0.001). We found prolonged tibialis anterior latency (fallers 158.8 +/- 23.7, controls 143.2 +/- 15.7 milliseconds, P = 0.03), marked losses in ankle strength (dorsiflexion: faller 3.2 +/- 2.9, controls 8.9 +/- 4.2 foot-pounds, P less than 0.001; plantarflexion: fallers 7.9 +/- 5.3, controls 21.4 +/- 11.1 foot-pounds, P less than 0.001), and decreases in range of motion (ankle plantarflexion: fallers 29.2 +/- 7.0, controls 37.8 +/- 12.4 degrees, P = 0.02). Gastrocnemius latency and electromyographic (EMG) measures of sequence showed no differences between fallers and controls. Sequence measures were not symmetric between the lower extremities in either fallers or controls. In this population of persons with unexplained falls who demonstrated substantial impairments in functional balance, effector factors appear more impaired than automatic postural responses. Alternatively, contemporary analysis of automatic postural responses may require further development before it can be useful to study balance problems in older persons.