In a car factory employing 203 women machinists making seat covers more women complained of respiratory symptoms after the introduction of a new seat cover fabric, cropped nylon backed with flame-bonded polyurethane foam (CNPF). 68 women working in the trim shop were studied on the first day back at work after a week's holiday and then at the end of a working week; the incidence of wheezing and/or shortness of breath was greater than expected but there was no difference between peak flow rates. A second study of 192 of the 203 women working in the trim shop confirmed this recent increase in incidence of asthmatic symptoms and showed that significantly more machinists who had worked with this new fabric had a reduced peak flow rate than machinists who had not. Asthma developed in one subject when she was working in the factory sewing CNPF, when she was handling this fabric in the challenge cabinet in the laboratory, and on challenge with toluene di-isocyanate in the laboratory. Airways resistance increased in 3 other workers after exposure to CNPF in the laboratory. Low concentrations (between 0.0003 to 0.003 ppm) of toluene di-isocyanate were found in the air around this fabric. 4 of 9 women with symptoms had IgE antibodies to toluene di-isocyanate.