We use an asymmetric 8-PSK signal set in a 4-state rate 2/3 Trellis-Coded Modulation (TCM) scheme for fading channels to show performance gain over known TCM schemes with symmetric and known asymmetric constellations. This scheme is an example of TCM schemes over fading channels where performance gain can be achieved at high SNRs, without increasing the minimum squared product distance, effective length or decreasing the multiplicity. Simulations for Rayleigh fading channels, using Monte Carlo simulation, are presented.