A simple experimental technique is described for the study of the onset of oscillation in a He-Ne laser. The risetime of the 6328 Å laser oscillation is found to be of the order of 100 μs and to be a function of gain. The results are analyzed using the Lamb semiclassical theory, and a value of

s is obtained for the time constant for population of the lower laser level. The significance of the results are discussed with respect to those of other workers.