MacT is a set of programs for the Apple Macintosh to construct and evaluate unrooted trees derived from amino acid sequences using a distance matrix method. Programs are designed on a 'one program-one task' basis for (i) determining the branching order in trees consisting of four or five species and calculating various statistical measures, (ii) calculating statistical measures for all possible topologis of unrooted trees; and (iii) generating and avaluating trees derived from bootstrapped samples. With four auxiliary programs unrooted trees can be build for maximal 26 species, and the robustness of topologies be tested by bootstrapping. MacT was written by Angela Luettke and Rainer Fuchs. A paper describing MacT has appeared in CABIOS 8 (1992), 591-594.