Estimates of the fraction of total land surface area under canopy openings (gaps) were made using four techniques: the fraction of total transect distance in gaps, the fraction of point-centered quarter points in gaps, the fraction of living and recently dead basal area in recently dead trees, and an estimate using line intersect theory based on the average diameters of gaps intersected. In general the four techniques produced similar results. The nature of the overall vegetation sampling scheme determines which of these techniques is most useful for a particular study. Forest Sci. 31:15-19.