Thirty people aged 64 and over living at home were asked to complete a “life-space diary” for 1 month during which they were invited to attend a gait laboratory for measurements of gait and balance. Twenty-eight subjects completed the diary satisfactorily, and 24 of these also undertook the laboratory tests. The diary was acceptable and gave a good indication of the subject's mobility. There was a close correlation between mobility as derived from the diary and the laboratory measurements of gait speed and mean sway path. The diary is worthy of further evaluation as an objective record of mobility in old people at home.