Laser studies dealing with various aspects of forest canopy measurement are reviewed. Aircraft LIDAR data have been used to estimate canopy density, tree heights, forest volume and biomass, to discriminate terrain units, and to add a height component to multispectral forest cover classifications. Linear comparisons between photogrammetrically-estimated canopy density and laser metrics indicate that the laser explains 45-65% of the variation noted in the photo estimates. Large variances are also associated with the relationship between laser canopy heights and the corresponding ground measurements. R-squared values on the order of 0.6 are typical; one study indicates that the laser height estimate will be within ±4 meters of the actual value 95% of the time. Estimates of woody biomass and volume are precise and repeatable between flightlines, however site-specific variation is high, limiting the use of the laser as a forest mapping tool. The laser metric-forest metric relationships are relatively coarse, due in part to 1) laser-ground misregistration errors; and 2) differences in the laser and ground sampling procedures. Integration of Global Positioning System data with the laser data stream, will, in the future, permit one to more accurately locate the laser transect on the ground, facilitating establishment of the necessary mathematical laser-ground relationships.