The program "sten.h2co.for" is a considerably modified version of the "sten.4.for" and other similarly named versions of the original STEN program that was written by N.Matthews in 1985/1986. A description of the original version can be found in Matthews[20]. This version can deal with all molecules for which collision rates and Einstein coefficients are available. Note that this version is still requires a 1-D spherically symmetric cloud, hence the retention of the old naming format. Many of these changes have however been incorporated into the ASTRA program that will be described later. The 1-D cloud structure has been retained here since this is still a valid model for many objects and a program that is written for spherically symmetric objects will always be many times faster than an equivalent program for more complex cloud shapes.