The binary frequency of IC 4665.

New radial velocity observations of 13 stars in IC 4665 indicate that the spectroscopic binary frequency in this cluster is 50 percent. It is suggested that the high frequency (95Th) previously found by Abt, Bolton, and Levy is a spurious one. The methods of detecting variable velocities and comparing binary frequencies are discussed and applied to IC 4665 and other clusters. On this basis, we conclude that the correlation between mean rotational velocity and binary frequency in clusters is marginal. Subject headings: clusters: open - stars: binaries - stars: rotation