The ageing process is accompanied by a loss of skeletal muscle bulk and mechanical slowing and also an increased risk of falling. Falls in the elderly cause substantial health and personal problems. Many of them occur for medically unexplained reasons. Establishing the mechanisms for these falls should lead to the development of effective intervention programmes to decrease the incidence of injurious falls. Decreased muscle strength, power output and also increased asymmetry of strength and power in the lower limbs have been suggested as possible causes of unexplained falls. However evidence for the role of asymmetry is limited (Skelton et al. 2002) and conflicting for strength (Lord et al. 1999; Schwender et al. 1977). Forty four healthy older people (76.1 ± 0.8 years (mean ± sem), 29 women) and 35 with a history of unexplained falls (75.9 ± 0.6 years, 30 women) participated in the study which had local ethical approval. They were all living independently in the community. Bilateral measurements of peak leg extensor power (Nottingham Power Rig) and the maximal voluntary contraction (MVC) isometric strength of the quadriceps and ankle plantar flexors (isokinetic dynamometry) were measured. A univariate general linear model (SPSS) with sex as a co-factor was used for analysis. Post-hoc Dunnett tests were used where appropriate (alpha = 0.01). In the fallers and non-fallers respectively the percentage difference between limbs was similar for the MVC of the quadriceps (11.4 ± 1.2 and 12.8 ± 2.0) and plantar flexors (19.9 ± 2.7 and 19.1 ± 3.3) and also for leg extension power (18.2 ± 3.1 and 13.9 ± 1.5). In view of the lack of differences between groups for limb symmetry, force data for the stronger limb are presented. Isometric strength was lower in the fallers than non-fallers for both quadriceps (335 ± 27 and 395 ± 21 N respectively, P<0.006) and plantar flexors (502 ± 49 and 643 ± 36 N, P<0.001). This was also the case for power output during leg extension (150 ± 12 and 180 ± 10 W, P<0.001). Isometric strength and power showed a strong association with falling, confirming recent findings. However, asymmetry does not appear to relate to falls risk.