The results of numerical simulations and experimental measurements are presented for the pressure dependence of the bistable voltage margin of an ac plasma panel cell. The measured dependence on gas pressure is correctly predictable only by modifying the previous theoretical models to incorporate a secondary emission coefficient for Ne+ 2ions which is about one-third the value for Ne+ ions. Further, the comparison between theory and experimental data indicates that the behavior of room temperature deposited MgO films can be explained by assuming a value of significant magnitude for the secondary emission coefficient for Ar+ ions. This value would have to approach zero if the behavior of panels made with films deposited at a higher substrate temperature of about 250°C are to be consistently explained. Finally, a critical evaluation is presented of the extent of the theoretical understanding of relevant physical phenomena involved in the bistable behavior of ac plasma panels. Copyright © 1981 by The Institute of Electrical and Electronics Engineers, Inc.