The rapid proliferation of complex plastic polymers and resins has led to a marked increase of work-induced asthma due to low molecular weight agents. Phthalates are frequently used in the manufacture of epoxy resins, plasticizers, adhesives and a wide variety of other materials. They have recently been identified as an important irritant and immunogen of at least four occupational respiratory syndromes, i.e., asthma/rhinitis, late respiratory systemic syndrome, pulmonary disease-anemia syndrome, and an irritant reaction. Isocyanates are extensively employed in the production of polyurethane foams, adhesives, paints and other plastic products. They have been incriminated in the causation of occupational lung disease since 1951. It appears that both specific IgE-mediated and non-specific irritant mechanisms are operative in isocyanate-induced asthma. Formaldehyde is a widely used irritating chemical, mainly employed as disinfectant or in the production of multiple resin products employed in the wood, shoe, and clothing industries. Several of these resin products can give off formaldehyde fumes causing occupational and non-occupational dermatitis, urticaria, bronchitis and reactive airway disease. Colophony pine resin used in virtually all soft soldering fluxes, and paraphenylene diamine used in the fur, paint and rubber industries have also been implicated in the generation of industrial asthma. Awareness of where such agents are likely to be encountered, together with patterns of respiratory disease induced, should facilitate earlier diagnosis.