MacP12 is a Macintosh program that allows simultaneous plotting of two protein property profiles selectable from 12 built-in amino acid property scales. Various parameters such as the region to be analyzed, the size of the sliding window, the weighting function and the size of the graphical output can be easily adjusted by the user, which makes the program appropriate for diverse research questions. MacP12 was written by Angela Luettke and Rainer Fuchs. A paper describing the program is in press and will appear in CABIOS 9, issue 6.