XMakemol is a program written for UN*X operating systems in ANSI C using the X, Xt and Motif libraries. It can be used to view and manipulate atomic and molecular data given in xyz format. XMakemol is a mouse-based application and many features can be accessed by clicking or dragging the mouse on the main window. Additional popup dialogs offer a number of additional features. Here is what an XMakemol session might look like. The system is a bucky ball and the Measure dialog is showing the measurement of bond-lengths, angles and a torsion angle. XMakemol can produce output in PostScript (black and white or colour)and in xpm format (which can be translated to gif format using xpmtoppm and ppmtogif). XMakemol can also produce a series of xpm files which can be translated into an animated gif file using the bundled utility xmake_anim.pl (formerly gmake_anim.pl). The one above is an animation of the "viagra" molecule (sidenafil).