This paper presents a method for evaluating the bit-error probability of a concatenated coding system for BPSK transmission over the AWGN channel, In the concatenated system, a linear Binary block code is used as the inner code and is decoded with the soft-decision maximum likelihood decoding, and a maximum distance separable code (or its interleaved code) is used as the outer code and is decoded with a bounded distance decoding, The method is illustrated through a specific example in which the inner code is a binary (64,40,8) Reed-Muller subcode and the outer code is the NASA standard (255,223,33) Reed-Solomon code over GF(2(8)) interleaved to a depth of 5, This specific concatenated system is being considered for NASA's high-speed satellite communications, The bit-error performance is evaluated by a combination of simulation and analysis, The split weight enumerators for the maximum distance separable codes are derived and used for the analysis.