Abstract
Krasno and Ivy have claimed that the change after sublingual nitroglycerin in the frequency at which a flickering light appears to fuse (f.f.f.) sharply differentiates between cardiovascular normals and patients with coronary and/or hypertensive disease and that this test may be useful in detecting and evaluating such disease. On the basis of a detailed analysis of the original publication and of data on 304 men these claims are denied. Indications for further study of flicker phenomena are discussed and fiducial norms are presented.