Exposure to isocyanates can be harmful to workers by causing different disorders of the airways. The main objectives of this study were to survey the personal 8 h time-weighted average exposure to isocyanates at 13 Swedish plants that handled either polyurethane, diisocyanates or both, including four types of manufacturing processes: moulding, continuous foaming, flame lamination and low or no heating processes. A total of 223 air samples were collected for 111 workers with personal air monitoring using a dry filter method with 1-(2-methoxyphenyl)piperazine (2MP) as derivatization reagent. A further 272 stationary samples were collected, using the 2MP method, a modified 2MP method and an impinger method using dibutylamine in toluene. With the applied strategy, a large number of workers were monitored and four industrial environments were compared regarding the isocyanate exposure. All workers were found to be exposed to isocyanates in the range 0.004–5.2 p.p.b. On average, the personal exposure levels in the different types of manufacturing processes were, in decreasing order: continuous foaming > flame lamination > moulding >> low or no heating processes. However, there were variations in exposure levels in plants with similar processes and also between different shifts performing the same tasks. Isocyanic acid, which could not be sampled by the 2MP method used for personal monitoring, was found by short-term stationary monitoring in levels up to 38 p.p.b. in the flame lamination plants.