We retrospectively analysed serial pulmonary function tests in 14 HIV infected patients receiving either bleomycin and vincristine or liposomal doxorubicin therapy (Doxil) for AIDS related Kaposi's sarcoma. There was a significant reduction in the carbon monoxide transfer coefficient in bleomycin treated patients compared with patients treated with Doxil. No other significant changes in pulmonary function, including the carbon monoxide diffusing capacity, were observed. These preliminary findings suggest that HIV infected patients with Kaposi's sarcoma, who are receiving bleomycin, may be at risk of accelerated pulmonary dysfunction. A larger prospective study should be performed to enable further investigation.