The technique of time-resolved resonance absorption spectroscopy was used to monitor the decay of photolytically produced CH radicals. Care was taken to ensure that any vibrationally excited CH, produced in the primary photolytic process, was relaxed co the ground state. Thus rate constants given in this work apply strictly for the removal of CN radicals in the absence of feeding by vibrational relaxation of higher levels, in contrast to previous work where this was not taken into account. For the first time, rate constants are reported for the reactions of CH radicals with the molecules N20, D200 NCI, DCl, CO2, H20, OCg, CO and HCN. No isotope effects were observed for the dauterated species. Rate data for the reactions of CN with 02, N0, H2, CH4 and C2H6 were also obtained and compared with previous data. The data show that recombination of CN radicals in the presence of both NO and CO occurs by a mechanism analogous to that for catalysed recombination of halogen atoms. A small negative activation energy (-10±4 kJ mol 1), characteristic of such processes, was calculated for the NO case. The reaction of CN with H2 vas also studied and compared with the CH case. However, it was not possible to state categorically that rate enhancement occurred with vibrational excitation, as vibrational to rotational energy transfer nay have bean important. Hence, only an upper limit of 1.7 is given for the rate constant ratio. A value of AN of (CH) - 417.6±1.3 W moll was determined using the equilibrium 293 content for the reaction CN + HCN C2N2 + H. This is in agreement with several recent results, reinforcing the need for a change in the currently accepted value. Work on the study of CA radicals in flames at Thornton Research Contra (Shell Research Ltd.), using the technique of resonance fluorescence, led to several practical suggestions for improving this technique, especially the use of a tunable dye laser to excite the CH radicals.