A 2 year old Chinese boy was reported in whom there was an association between usual interstitial pneumonitis (UIP) and serum antineutrophil cytoplasmic antibody of the classical cytoplasmic type (cANCA). The concentration of cANCA reflected disease activity and decreased during a 6-week course of prednisolone. The gallium lung scintiscan index correlated with his disease activity. Both the serum cANCA concentration and the gallium lung scan could be used to monitor responses to treatment in this patient with UIP.