Three related studies at the Carnegie Museum of Natural History and the University of Pittsburgh examine effects of the organophosphate insecticide DDVP (dimethyldichlorovinylphosphate). The first tested its effectiveness on all stages of the beetle <i>Dermestes maculatus</i> in museum storage case environments. The second study observed the diffusion of the insecticide within storage cabinets and the influence of temperature, relative humidity, and the nature of the materials stored on its insecticidal effectiveness. The third study concerned the effects of DDVP on a wide range of materials involved in stored museum collections as revealed by visual analysis, weight changes, and pH shifts.