The L-Neuron (LN) program is written in plain “ANSI” C, and it is portable to many platforms. The results shown here were obtained on a Pentium PC under Windows 95. An identical version of LN has been compiled in a Unix environment (on an SGI Origin 200 under Irix 6.5). LN can run under DOS or in a Unix shell environment, but a user interface (programmed in Delphi) is available for Win95, based on a modification of Lichti’s Lsys32. LN reads a list of neuroanatomical parameters and outputs a turtle graphic L-system string. Anatomical parameters are in the form of statistical distributions (gaussian with average, standard deviation, and minimum; uniform with min and max; or constant), and actual values are sampled stochastically within these distributions. The program makes use of three alternative neuroanatomical algorithms (Hillman’s, Tamori’s, Burke’s). The source code is based on a modification of Laurens Lapres’ “L-parser”, a freeware application to generate L-systems. The turtle graphic “dialect” of LN is thus identical to that of L-parser. Lapres’ graphic application “L-viewer”, included in the L-parser package, can be used as is for LN. LN can output files in several other graphic formats, as well as in the “xyzd” neuroanatomical standard, which is compatible with Genesis, Neuron, ArborVitae, and Southampton’s Cell Viewer. The neuroanatomical parameters used by LN can be obtained directly from the literature or measured from experimental tracing xyzd files. Other “emergent” neuroanatomical parameters can be measured from both the experimental neurons and the LN-generated virtual neurons in the xyzd format.