Repeated spectroscopic observations of all eight W-R stars in the SMC are reported. Two of the stars are of the late, cool WN subclass, with one possibly an extreme Of star. One is definitely, the other probably, constant in radial velocity. Five early, hot WN (WNE) stars all exhibit O-type spectral lines. Four of these stars are definitely spectroscopic binaries. The eighth star belongs to the rare oxygen seqeunce WO and has an orbiting O4 V companion. The binary frequency of the six hydrogen-poor WNE/WO stars appears to be high, but cannot be called abnormal. SMC W-R stars appear to have more massive progenitors than do Galactic W-R stars. Spatial correlations of spectral subclasses for the SMC W-R population are compatible with the evolutionary scenario WNL - WNE - WCE/WO in a low-metallicity environment, with most W-R stars appearing in the bottleneck WNE phase. 28 references.