THE ninth magnitude BOIb star HDE 226868 is closely coincident with the position of Cygnus X-1 and its associated variable radio source1. Dolan2 has pointed out that Cyg X-1 appears to be a two component X-ray source. One component has a synchrotron spectrum, and the other has a thermal (or bremsstrahlung) spectrum. The latter component varies on a time scale of days in a way that suggests it is being eclipsed. Therefore I decided to take photographic spectra of HDE 226868 to look for velocity and spectrum variations that might be correlated with the X-ray fluctuations. I find that the velocity of the star varies with a period consistent with that of the X-ray variation. It may not be possible, however, to interpret the X-ray variations in terms of simple eclipses.