Abstract: The concept of integrating natural enemies and pesticides into a practical IPM program dates back to some of the original ideas that framed the development of the IPM paradigm (Stern et al., 1959). The IOBC recognized the need for this when it formed the working group (WG) Pesticides and Beneficial Organisms in 1974 ‘to identify selective pesticides for beneficial arthropods and to promote their use, in order to enhance biological control in plant protection…’ With this WG as a driver, numerous publications and data bases (both public and private) have been developed on the side effects of pesticides. The question to ask is “Have these data and databases made a difference in terms of the practical combined use of natural enemies and pesticides in the greenhouse environment? Clearly they promote the use of more ‘selective’ products, but are these really being integrated with natural enemies? In 2000, Van Lenteren stated ‘greenhouse crops will be produced without the need to use conventional pesticides in the very near future’. We are far away from that goal, especially in greenhouses devoted to production of ornamental crops. The increased focus on the development of biopesticides has presaged an era with greater hope for compatibility with natural enemies but this is falling short of expectations. In 2011, biopesticides accounted for < 10% of total pesticide use in California agriculture. The future still looks encouraging for these products, but there is a long way to go (Glare et al., 2012). We have taken a 'field' approach to evaluate compatibility by examining endemic natural enemies that move into California greenhouses. The premise is that in the absence of sprays, or where less offensive sprays are applied, there should be larger populations of this endemic fauna in greenhouses. Our focus is on a predatory fly (Coenosia attenuata Stein) and an obligate powdery mildew predator (Psyllobora vigintimaculata Say); other natural enemies are also being surveyed.