Experiments on natural convection mass transfer adjacent to vertical and upward-facing inclined plates were performed by employing an electrochemical technique. Local measurements were made, yielding both streamwise and spanwise mass transfer distributions. Time-dependent mass transfer rates were measured in the transition and turbulent regimes. The measured local laminar mass transfer coefficients agreed very well with analytical predictions, both for vertical and inclined surfaces. The Rayleigh number marking the onset of laminar-turbulent transition varied markedly with the angle of inclination, decreasing with increasing departures from the vertical. In the transition regime, for surfaces inclined at angles greater than 15 degrees to the vertical, significant spanwise variations in both the instantaneous and time-averaged mass transfer rates were in evidence. The timewise fluctuations of the turbulent mass transfer rates were of substantially greater amplitude and period for inclined surfaces than for the vertical plate. The time-averaged, local turbulent mass transfer coefficients were correlated with the one-third power of the Rayleigh number and, in addition, exhibited an appreciable dependence on the inclination angle.