The reaction C( 3 P J )+C 2 D 2 (X 1 Σ g + )->C 3 D+D( 2 S 1 / 2 ) has been studied with pulsed, crossed, supersonic molecular beams, in the range of relative translational energies t r =4-240 meV. The D( 2 S 1 / 2 ) product has been detected by laser-induced fluorescence. The reaction is found to be slightly exoergic, with no barrier. Relative integral cross-sections are proportional to ( t r ) - 0 . 7 2 + /- 0 . 0 3 below t r =50 meV. These findings, along with energetics considerations, suggest that the analogous C( 3 P J )+C 2 H 2 (X 1 Σ g + )->C 3 H+H( 2 S 1 / 2 ) reaction is also a barrierless process.