Observational data for 1493 flat edge-on RFGC galaxies are processed to determine parameters of relativistic models of their collective motions. Unfortunately, the results for the complete relativistic model turned to be inadequate. Values of components of involved tensor S are overestimated by two orders of magnitude due to peculiarities of least-squares method. The semirelativistic model obtained by discarding this tensor is free from this flaw and is characterized by the low bulk motion module D = 70...230 km/s. All characteristic parameters for galaxies distances estimation and for their collective velocity field are calculated for nonrelativistic and for two variants of relativistic and semirelativistic models.