Emphasis has recently been placed on the roles of chemotactic cytokines called chemokines to explain the accumulation of inflammatory cells in the lung that may precede or accompany pulmonary fibrosis in interstitial lung diseases. We hypothesized that RANTES, a member of the C-C chemokines, is one such chemokine. Bronchoalveolar lavage was done in 20 patients with sarcoidosis, 10 patients with interstitial pneumonia associated with collagen vascular disease (CVD-IP), 10 patients with idiopathic pulmonary fibrosis (IPF), and eight healthy volunteers (HV), all of whom were never-smokers. We semiquantitated the spontaneous RANTES mRNA expression by a competitive reverse transcription-polymerase chain reaction (RT-PCR) technique, and measured the levels of RANTES protein by enzyme-linked immunosorbent assay. In all disease groups the expression of RANTES mRNA by bronchoalveolar lavage fluid (BALF) cells and the levels of RANTES protein in BALF were significantly increased compared with those in HV. Patients with sarcoidosis and CVD-IP had a significant positive correlation between the expression of RANTES mRNA by BALF cells and BALF lymphocytosis. The amounts of RANTES mRNA expressed by peripheral blood mononuclear cells and the levels of RANTES protein in serum did not differ among all study groups. Our study demonstrates the adaptability of a semiquantitative RT-PCR method for determining cytokine mRNA expression in vivo. Our results suggest that RANTES may be one of the chemokines that are involved in the mechanism for the accumulation of inflammatory cells in the lung of some distinct interstitial lung diseases.