RELATEDNESS 4.2 Relatedness 4.2 is a Macintosh program for calculating genetic relatedness and F-statistics using single-locu, codominant markers. The program reads data from tab-formatted text files (like those generated by Microsoft Excel or other spreadsheets in Text-only mode), and allows up to 6 demographic variables for use in specifying the particular subsets of individuals to be compared. 3 of these variables are pre-defined (deme, group, and sex), and the other 3 are user-defined to hold whatever data the user wants. The program can currently accept genetic data of up to 25 loci with 25 alleles at the most polyallelic locus. Upcoming upgrades will expand these limits; registered users will be notified when upgrades are available. The program has been tested on a wide range of Macintosh models from the old 512K version to the AV series Quadras. It runs under System 6.x and 7.x. The file RLAT.hqx decodes (with Binhex 4.0) to form a self-extracting archive which includes the application, its defaults file, the manual, a Tutorial data set, and instructions for the Tutorial. The file may be distributed freely. If you publish results using the program, please cite Queller & Goodnight 1989; the reference is given in the manual. Questions & comments to Keith Goodnight or Dave Queller. keithg@whittaker.rice.edu queller@pop.rice.edu