THE RADII OF 62 CLASSICAL CEPHEIDS

Based on dense series of photoelectric observations and on our radial- velocity measurements, we calculated the radii of 62 northern Cepheids by Balona's method. We derived the following period-radius relation: log R = 1.23(+/-0.03) + 0.62(+/-0.03) log P. Our detailed analysis sho ws that the distance scale for Cepheids cannot be refined using their radii by an independent method which is unrelated to the distances to young open clusters because of the random and systematic errors of the Baade-Wesselink technique.