We described longitudinal changes of movement performance in a population-based sample of women followed from age 70 to 78. We also studied the cross-sectional relationships between medical conditions and movement performance at baseline, and longitudinal relationships between baseline medical conditions and changes of movement performance. Two hundred and thirty-four women aged 70 years participated in the baseline study, and 88 women participated in a follow-up study 8 years later. Movement performance was measured by an optoelectronic test, the postural-locomotor-manual (PLM) test, which objectively and precisely measures the subject's mobility of lower and upper extremities. Information on medical conditions including selected diseases and symptoms were obtained by self-report and/or by physical examination. Movement time (MT), an indicator of the overall movement performance of the PLM test, increased over 8 years. This change was mainly related to prolonged duration of the locomotor phase (walking forward), but not to the duration of the manual phase (goal-directed arm reaching). At baseline, poor PLM performance was related to hypertension, orthostatic hypotension, cerebrovascular diseases, chronic bronchitis, depression, arthritis, dizziness, chest pain, dyspnea, joint problems, leg pain, tiredness, number of diseases and number of symptoms at baseline. Increased MT during follow-up was associated with arthritis and dyspnea at baseline, and newly developed diseases during follow-up. Our study results indicated that 70-year-old women had a general slowing of their movement performance over 8 years. Age-related decrements of movement performance were more striking in the lower extremities than in the upper extremities. Arthritis and dyspnea at baseline, and incident diseases during follow-up were related to this age-related decline of movement performance.