Diversity reception using a postdetection maximal-ratio combiner (MRC) was experimentally investigated for π/4-shift QDPSK signal transmission in Rayleigh fading environments. Two-branch postdetection MRC diversity reception provides a diversity gain, for a required Eb/N0, of about l.5dB over selection diversity. It is also effective in reducing the impact of multipath channel delay spread. The average BER due to delay spread can be further reduced by a factor of about 1-5 times from selection diversity.