In this paper, we investigate time-reversal space-time block codes (TR-STBCs) and receive diversity for complementary code keying (CCK) modulation, which is employed in the wireless local area network (WLAN) standard IEEE 802.11b. The construction of TR-STBCs from orthogonal space-time block codes designed for flat fading channels for an arbitrary number of transmit antennas is discussed. Furthermore, an equivalent single-input single-output (SISO) transmission model for CCK is derived, which combines the effects of space-time coding and multiple receive antennas. For indoor multipath fading channels numerical results are provided for TR-STBCs with two and three transmit antennas, which demonstrate that significant gains can be obtained compared to a SISO transmission. For detection, decision-feedback equalization (DFE) and reduced-state sequence estimation (RSSE) especially tailored for CCK transmission are considered.