We have obtained velocity-resolved spectra of the 12C II 157.8 microns 2P3/2-2P1/2 fine structure line in the M42 region of Orion. Observations at 0.8 km s-1 resolution with a laser heterodyne spectrometer show multiple velocity components in some locations, with typical linewidths of 3-5 km s-1. Spectra of theta 1C and BN-KL also show weak emission from the F = 2-1 hyperfine component of the equivalent 13C II line. From the observed 12C II/13C II line intensity ratios, we deduce that the 12C II emission is optically thick with tau approximately 5 at both positions. Excitation temperatures of 128 K and 90 K, together with column densities of approximately 1 x 10(19) cm-2 and approximately 4 x 10(18) cm-2, are derived for theta 1C and BN-KL, respectively.