A sensitive 10° × 15° 13-cm map made of the CMa OB1 H II regions' radio emission shows a strong similarity to Hα emission photographs. Sharpless 296 is shown to consist of a prominent central and western arc completed by a weaker southern loop, and with a faint northern bar. The emission is thermal, superimposed over a predominantly non-thermal back-ground. The H142α recombination line has been detected at eight positions in S296, and in S292 and S297. The average electron temperature in S296 is 6900 ± 1300 K. The UV fluxes from the CMa OB1 stars account for the observed emission measures of the Hn regions. The H142α 1sr velocities indicate that the ionized material is in contact with the molecular clouds.