Dietary protein requirements of elderly people were determined by short-term nitrogen-balance techniques and using calculations recommended by the 1985 Joint FAO/WHO/UNU Expert Consultation. Twelve men and women aged 56-80 y were randomly assigned to groups that consumed either 0.80 +/- 0.01 or 1.62 +/- 0.02 g protein.kg-1.d-1 (mean +/- SEM). Net nitrogen balance was negative for the lower-protein group (-4.6 +/- 3.4 mg N.kg-1.d-1) and positive for the higher-protein group (13.6 +/- 1.0 mg N.kg-1.d-1); the intake required for nitrogen equilibrium was estimated to be 1.00 g.kg-1.d-1. Nitrogen-balance data from three previous protein requirement studies in elderly people were recalculated by using the same balance formula and combined with the current study data to provide an overall weighted mean protein requirement estimate of 0.91 +/- 0.043 g.kg-1.d-1. Together, the current and retrospective nitrogen-balance data suggest that the mean protein requirement in elderly adults is considerably greater than the 0.60 g.kg-1.d-1 established by the 1985 Joint FAO/WHO/UNU Expert Consultation. A safe protein intake for elderly adults would be 1.0-1.25 g.kg-1.d-1 of high-quality protein.