When two biological simulations on evolution and genetics (one originally developed for a conventional university undergraduate course) were introduced into Open University distance education classes, the difficulties encountered required a reappraisal of the concept of using computer simulation for distance learning and decisions on which simulation features were essential and which were merely desirable. The evolution course adapted a simulation called EVOLVE, which models the genetic and evolutionary consequences of two populations of a single flowering plant species coming together after a period of genetic isolation. The second simulation, WHEAT, models the inheritance of height in wheat for an experiment which biometrically analyzes the inheritance of a continuously varying character. To overcome problems of limited access to computer terminals and the need for cost-effective, interactive computing at remote sites, both a fully interactive and a non-interactive version of EVOLVE and a non-interactive but stochastic version of WHEAT were developed. Although the interactive element of computer assisted learning (CAL) was lost entirely in overcoming serious logistical problems, the resulting non-interactive programs have provided a tolerable compromise and, in the case of WHEAT, perhaps even a superior approach than if interactive terminals were used. Eight references are listed. (LMM)