During the formation of peribronchial fibrosis in asthma, remodeling of connective tissue is due to an increase in deposition of extracellular matrix components like that of specific types of collagens and proteoglycans. By taking bronchial biopsies, we were able to isolate cell cultures derived from asthmatic patients and healthy volunteers, which provides a good model system to study differences regarding cell morphology and key connective tissue proteins in the remodeling process. Proteomics, utilizing two-dimensional electrophoresis and modern image analysis systems have made it possible to study protein expression and regulation of proteins in biological systems. By using this powerful tool, it is possible to quantitatively study protein regulation and to obtain increased knowledge about the mechanism behind the inflammatory process and formation of peribronchial fibrosis. We have optimized a proteomic protocol enabling detailed investigation of the protein expression pattern in human lung cells. An increased expression pattern was obtained, whereby 20 protein spots could be detected by image analysis in the <45 kDa region. Out of these, specific regulations of four spots were found by quantitative image analysis and spots of interest were identified by MALDI TOF-MS. This protocol enables us to study 1000--2000 proteins simultaneously and the possibility to correlate protein expression to the physiological status of the cell culture investigated. We have found that two proteins, actin and tropomyosin, are increased in expression due to transforming growth factor-beta stimulation. These proteins are correlated to the transformation of normal fibroblasts to myofibroblasts which are involved in the remodeling processes observed in asthma.