Following is a fuller description of the Quercus program set: Shaw (1987; Evolution 41: 812-826 and 1991; Evolution 45: 143-151) and others have presented a maximum-likelihood approach to quantitative genetic analysis. This approach provides estimates of fixed effects and components of variance for a polygenic model fitted to data on phenotypic values for individuals whose genetic relationships are known. The current programs have the capability of handling multivariate data of diverse genetic designs, spanning the range of standard mating schemes (offspring-parent, nested, factorial, diallel, regardless of balance). The programs permit tests of the hypothesis that any particular component (or set of components) of variance or covariance equals zero. In addition, there is a program that tests the hypothesis that two G matrices are the same. Efficiency of the current programs (i.e. requirements of computer memory and time) has been greatly improved over that of the previous versions. Data input has been made more flexible and diagnostics have been implemented in order to avoid and/or clarify runtime errors. The programs are written in standard Pascal and are distributed as source code. They have been run successfully on Sun and DEC workstations, VAX and IBM mainframes, and a Cray Y-1 supercomputer. This work has been supported by grants from NIH (GM09664-02) and NSF (BSR 8817756, BSR 8905808, and DIR 9112842). If you obtain files from the quercus set, please send your name and address, including e-mail address, to notify us. Ruth G. Shaw Department of Ecology, Evolution, and Behavior University of Minnesota St. Paul, MN 55108 shaw@superb.ecology.umn.edu, rshaw@ecology.umn.edu, rshaw@vx.cis.umn.edu Frank H. Shaw Institute for Mathematics and Its Applications University of Minnesota Minneapolis, MN 55455 fshaw@ima.umn.edu, fshaw@superb.ecology.umn.edu