The total quenching rate constants for NCl(a(1)Delta) molecules were measured at room temperature for 40 molecular reagent species and for F, H, N and O atoms. The Cl + N-3 reaction was used to provide the NCl(a(1)Delta) molecules in a room temperature flow reactor; the azide radicals were obtained from the F + HN3 reaction. In most cases, rate constants were obtained for both NF(a(1)Delta) and NCl(a(1)Delta) so that the data could be confirmed by comparison with earlier studies of NF(a(1)Delta). The quenching rate constants for NCl(a(1)Delta) range from similar to 1 x 10(-15) to 4 x 10(-11) cm(3) molecule(-1) s(-1). Except for O-2, F, H, CH3Cl, HCl, HBr, and HI, rate constants for the NCl(a(1)Delta) molecule are generally smaller than or comparable to those for NF(a(1)Delta), and NCl(a(1)Delta) is not especially reactive at 300 K. Small rate constants were obtained for common gases, such as H-2, CO2, and CH4; the rate constants are larger for unsaturated hydrocarbons and they increase with the number of carbon atoms in the molecule. A correlation was found between the basicity of a series of amines and magnitudes of the quenching rate constants for NF(a(1)Delta) and NCl(a(1)Delta); the smaller NCl(a(1)Delta) rate constants indicate a less acidic nature for NCl(a(1)Delta). An unusual concentration dependent, wall-quenching process was found for (CH3)(2)O, CH3OH, OCS, and saturated hydrocarbons that affected the NCl(a(1)Delta) decay kinetics, but not those for NF(a(1)Delta). The interaction between NCl(a(1)Delta) and NF(a(1)Delta) was qualitatively studied; the total bimolecular destruction rate is no larger than those for NCl(a(1)Delta) or NF(a(1)Delta) alone. The energy-pooling process between NF(a(1)Delta) and NCl(a(1)Delta) mainly gives NF(b(1)Sigma(+)) + NCl(X(3)Sigma(-)).