Five iminyl radicals, R2C=N (R = t-Bu, 1-adamantyl, i-Pr, CF3, and C6H5), have been generated by photolysis directly, in the cavity of an epr spectrometer, of solutions of the parent ketimines in di-tert-butyl peroxide. At -35° the rate constants for the bimolecular self-reactions to form the corresponding azines are 4 × 102 (t-Bu), 5 × 104 (1-Ad), 4 × 107 (i-Pr), 2 × 108 (Ph), and 4 × 109 M-1 sec-1 (CF3). At temperatures above -25° (t-Bu)2C=N undergoes a first-order decay. This reaction is a β scission and yields pivalonitrile and a tert-butyl radical. The rate of this β scission is compared with the rates of β scission of structurally analogous alkoxy radicals.