Low-temperature kinetics of the reactions of C2H radical with ethene (k(1)), propene (k(1)), and 1-butene (k(3)) are studied using a pulsed Laval nozzle supersonic expansion. The C2H decay profiles in the presence of both the alkene reactant and O-2 are monitored by the CH(A(2) Delta) chemiluminescence tracer method. The rate constants k(1), k(2), and k(3) are measured at T = 103 K to be (1.4 +/- 0.4) x 10(-10), (2.4 +/- 0.6) x 10(-10), and (2.6 +/- 0.6) x 10(10) cm(3) molecule(-1) s(-1), respectively. Measurements at room temperature (296 K) and previous data suggest a slight negative temperature dependence for all three reactions.