Near-saturation pressure, density, and temperature (P,rho,T) and vapor-pressure measurements for NH, are reported over a temperature range from 279 to 392 K. Liquid-phase isothermal (P,rho,T) and bubble-point-pressure measurements for two standard mixtures of NH3 + H2O (x(NH3) = 0.8360 and 0.9057 mole fraction) are reported over a temperature range from 280 to 379 K and at pressures to 7.7 MPa. These data are compared to literature data and correlations and agree within +/-3% for bubble-point pressures, +/-0.005 g/cm(3) for liquid densities, and +/-0.0011 g/cm(3) for vapor densities. A consistent data set for equation-of-state optimization at high concentrations of NH3 is proposed.