A FORTRAN program is given for calculating the average run length (ARL) of a zone control chart with zone scores specified by the user. The program has two parts. The first part of the program allows the user to input zone scores, and then constructs a matrix of transition probabilities based on a Markov chain representation of the control chart. The second part of the program uses this transition matrix to determine the ARL of the chart for any specified shift size, where the shift size is expressed in standard error units. The program then gives this ARL as output.