Laser flash photolysis (LFP, XeCl, 308 nm) of 11,11-dibromotricyclo[4.4.1.0(1.6)]undeca-2,4,8-triene (1) or 10,10-dibromotricyclo[4.3.1.0(1,6)]deca-2,4-diene (2a) produces CBr2 and an aromatic compound. Bromochlorocarbene is produced by LFP of 10-bromo-10-chlorotricyclo[4.3.1.0(1,6)]deca-2,4-diene (2b). The carbenes are trapped by pyridine to form ylides. The lifetimes of CBr2 and CBrCl and their absolute reactivities toward pyridine and alkenes have been determined. The relative reactivity of CBr2 toward alkenes determined by LFP methods is in excellent agreement with that determined previously by chemical analysis of reaction mixtures, and the rate constant data reveal that the absolute reactivity of CBrCl more closely resembles that of CBr2 rather than that of CCl2.