By symmetry analysis of Me& superstructures observed experimentally in carbides, the MeC, SI-Me6CS order-disorder phase-transition channels have been determined. For the superstructures examined using the static-concentration-waves method. the distribution functions of carbon atoms have been calculated. It is shown that an Me6C5-type atomic ordering is described by several long-range order parameters. The regions of admissible values of the order parameters have been determined for each of the superstructures treated.