In recent studies, daily physical activity ratios (PARs) greater than the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) reference value of 1.5 have been reported for elderly men and women. The purpose of this study was to investigate whether a high PAR in elderly subjects can be explained by a higher energy cost of physical activities (EEact). To this end, 12 elderly women aged 69 to 82 years, completed physical activity diaries during a 2-day stay in a respiration chamber. From these diaries, total daily energy expenditure (TEE) in the calorimeter was estimated (TEEfac) using FAO/WHO/UNU PARs for physical activities and measured resting metabolic rate (RMR). TEEfac was 7.0 +/- 0.9 MJ/d (PAR, 1.35 +/- 0.06). TEE was also measured in the chamber (TEEcal) and was 8.3 +/- 1.3 MJ/d (PAR, 1.60 +/- 0.16). TEEfac was 14.8% +/- 8.1% lower than TEEcal. To investigate whether the underestimation of TEEcal was due to a higher EEact in the elderly women as compared with the FAO/WHO/UNU references, EEact of six specific activities ranging from sitting at rest to walking on a treadmill at self-chosen speed was measured with a ventilated-hood system. Individually measured PARs of the six activities were similar to FAO/WHO/UNU reference PARs. This study suggests that in elderly women a high TEEcal is not explained by EEact during nonstandardized physical activities performed at self-chosen speeds. Whether these results can be extrapolated to the free-living environment needs to be investigated further.