Details of a novel technique for direct real-time measurement of the primary radical concentrations generated in pulsed laser photolysis (PLP) experiments ate presented. The method takes advantage of the large increase in fluorescence quantum yield that occurs when a nitroxide containing a suitable fluorophore couples with a carbon-centered radical. The technique is applied to PLP experiments which involve photolysis of azobisisobutyronitrile (AIBN) or azobis(methyl isobutyrate) (AIBMe) in the presence of 4-(1-naphthoyloxy)-2,2,6,6-tetramethylpiperidine-1-oxyl (NTEMPO). In these experiments, the method is shown to be capable of reliably measuring transient radical concentrations of less than 10(-7) M. Various side reactions that might complicate the technique are considered and shown not to be of significance. The concentration of radicals generated per pulse is shown to have a linear dependence on [AIBN], [AIBMe], and laser energy per pulse (and is shown to be independent of [NTEMPO]) over a wide range of conditions encompassing those typically encountered in PLP polymerization experiments. The concentration of radicals generated per pulse increases with increasing temperature, reflecting changes in the quantum yield for radical generation. The rate of intramolecular fluorescence quenching of NTEMPO in benzene was determined to be in the range 2-4 x 10(10) s(-1).