Studies are now in progress on the nature of various possible systematic and random errors which may be influencing the values of the Hubble parameter Ho derived from application of the Tully-Fisher method to samples of cluster spirals outside of the Local Supercluster. Three effects seem to be of most importance. (1) Clusters yield slopes in the infrared Tully-Fisher diagram varying from 8 to 12, making it problematic as to how to derive a relative distance modulus from comparison with the local calibrators, (2) errors in measured 21-cm line widths (often measured at low signal-to-noise ratios) are the dominant source of error in derived relative distances, (3) errors in measured optical major and minor axes of a galaxy influence both its derived inclination and the H-magnitude as corrected to a standard isophote. Monte Carlo simulations of cluster samples, however, have shown that the tendency not to detect H I from edge-on and/or low-luminosity galaxies introduces no important biases. Overall, the relative distance of any of these clusters to the local calibrators appears to be good to ±20%.