Stellar winds from hot supergiants

High-dispersion spectrographic data are described for 65 very luminous galactic OB stars. Their absolute magnitudes and masses are estimated. Almost all the stars show evidence for mass outflow, and the flow rate is empirically calibrated from mass-loss models for a few of them. Approximate contours of mass-loss on the H-R diagram are suggested which support the zero point of the individual rates. These are as high as one hundred-thousandth of a solar mass per year from a supergiant of 60 solar masses. Anomalously high mass-loss rates found in a few stars may be connected with duplicity of the objects.