The fully developed incompressible turbulent boundary layer in a channel has been explored using constant-temperature hot-wire anemometry. Particular attention was paid to measurements well into the viscous sublayer, yielding results which are believed to be new. Frequency spectral analyses of the fluctuating velocity components have been obtained for the inner layers. The mean velocity distribution in the sublayer has been determined with sufficient accuracy for a reasonable estimate of skin friction to be made. The results are compared with those of Laufer [11] and Comte-Bellot [4].