The gas-phase reactivities of ground-state chromium dimers (Cr2 (X 1∑g +)) for three small molecules (02, NH3, and C2H4) were investigated in a mass-flow controlled cell. The transient concentration of Cr2 (X 1∑g +, v = 0) produced by pulsed 266-nm laser photolysis of [Cr(CO)6] was monitored by a time-resolved laser-induced fluorescence (LIF) at 459.67 nm (A 1∑u +, v″ = 0 ← X 1∑g +, v′ = 0). The pseudo-first-order decay rates of Cr2 (X 1∑g +) were observed to increase linearly with increasing O2 and NH3 pressure, giving pseudo-second-order rate constants of (2.3 ± 0.3) × 10-11 cm3 molecule-1 s-1 for Cr2 + O2 and (4.3 ± 0.8) × 10-13 cm3 molecule-1 s-1 for Cr2 + NH3 under 6.0-Torr total pressure with Ar buffer gas at room temperature. On the other hand, C2H4 was apparently found not to react with Cr2 (X 1∑g +) under our experimental conditions. In the Cr2 + O2 reaction, the pseudo-second-order rate constants were found to depend on the total pressure, and the limiting low-pressure rate constant was estimated to be (5.9 ± 2.5) × 10-28 cm6 molecule-2 s-1.