Abstract: The invention provides spectroscopic methods for detecting helicase activity and inhibitors of helicase activity. Samples are assayed for helicase activity by: (a) incubating a mixture of the sample, double-stranded nucleic acid and a suitable luminescent marker which lumineses selectively in the presence of double-stranded nucleic acid; (b) exposing the mixture to light capable of inducing luminescence from the marker; and (c) detecting the intensity of luminescence from the mixture. Alternatively, samples are assayed for helicase inhibitors by further including in the mixture a helicase and incubating the mixture under conditions whereby, but for the presence of an inhibitor of the helicase in the sample, the helicase would be capable of converting a portion of the double-stranded nucleic acid into single-stranded nucleic acid. In both assays, helicase activity is inversely proportional to the detected luminescense. The methods are particularly suited to high-throughput drug screening.