The Weibull distribution has been used in many areas of forestry research. Complete Weibull distributions have been used to describe individual tree mortality (Glover and Hool 1979), stand level mortality (Somers et al. 1980), seed germination (Bonner and Dell 1976, Rink et tl, 1979), and tree height and diameter distribution in forest stands (Bailey and Dell 1973, Hafley and Schreuder 1977, and others). Computer programs to estimate parameters of the complete Weibull distribution when the data are complete are readily available (Bailey 1974, Schreuder et al. 1978). Sample data for some applications may be censored or truncated rather than complete. The program WEIBUL was prepared to allow estimation of complete or truncated Weibull distribution parameters from several types of censored or truncated data.