There is often some dispute in the literature as to whether a particular Cepheid (S Vul, for example) belongs to Type I or Type II. JHK photometry has been used to calculate Baade-Wesselink radii for a number of stars always, sometimes or occasionally stated to be Type II Cepheids. Radial velocities have been taken from the literature.

The (K, J – K) radius of SW Tau is 8.30 ± 0.34. This is about half of the expected radius for a Type I Cepheid at this period and normal for Type II.

For V553 Cen, the relative phasing of radial velocities and infrared photometry has to be done by choosing a relative phasing where the phase shift between the radius displacement curve integrated from the radial velocities and the photometric radius displacements is minimized, and where the surface brightness coefficient A (Balona 1977) is normal for a star with the colour indices of V553 Cen. Uncertainty in the reddening has a negligible effect on the radius solution obtained in this way. I have also considered the degree to which the K, J – K and K, V – K solutions give similar answers, as the relative phasing of the optical photometry and the radial velocities was more straightforward. The (K, J 73x2013; K) radius is 11.2 ± 0.4, normal for a Type II Cepheid.