title: Erratum.
abstract: In the article "the 0.001557806449023-Second Pulsar" by M. Mitchell Waldrop (Research News, 18 Feb., p. 831), the last sentence of the last full paragraph in the second column should have read: "Within a few weeks he was in Aricebo himself, and on 14 November he verified pulses at an astonishing 642 hertz, equivalent to a period of 1.558 milliseconds."