Isocyanates are used extensively worldwide in the production of different foams and elastomers. They also serve as glues, and lacquering and coating materials. Their improper application can result in inhalation exposure and sometimes also cutaneous absorption. The main hazardous effects are obstructive airway diseases. This review above all presents little-known sources of exposure in industry, pathological reactions to this exposure, and recently published approaches for solving the problem (International Consensus Report on Isocyanates). In addition, there is a need for the establishment of a validated biomonitoring system for potentially exposed employees.