The MLAB interactive mathematical modeling language is intended to serve biomedical researchers. It has been implemented by Civilized Software for IBM-compatible personal computers. MLAB may be used to perform complex mathematical and statistical calculations, including curve fitting to differential equation models, by means of simple, direct computational commands. functions, data, and computational results may be displayed graphically on screen using powerful graphics commands. Graphs so constructed may also be converted to a disk file for transmission to a Postscript laser printer for inclusion in a word- processing document, allowing inclusion in scientific articles. MLAB has shown itself essential in health-related research, as demonstrated by its use in hundreds of publications, and continuing interest in its use at the National Institutes of Health, medical research institutions, and pharmaceutical companies. The objective of this proposal is to convert and enhance the MLAB program to run on the Apple Macintosh II family of computers. while the initial conversion to be carried out for Phase I will be equivalent to the PC program in most ways, the Phase II product will have new features, including animated graphics, and fully incorporate the Macintosh graphical user interface to increase the power and simplify use of the MLAB program. For Phase I we will also design (subject to revision and enhancement during Phase II) some of the extensions to MLAB which take advantage of the Macintosh graphical user interface. These features will include manipulable graphics windows which permit graphs to be edited using the mouse and pull-down menus to change font, size, color, and position of text labels, to re-size and re-window the graphs, and to produce hard copy. Within graphs, curves may be identified with the mouse for the purpose of deletion, extracting information, removing suspicious data, as well as changing color, plotting characters, and labels.