In the previous experiment, it was found that the application of illite in both forms of particulate and powder as the soil conditioner was effective in the stimulated growth of lettuce, especially at its early growth stage and as powder form. The identification of effective proteins involved in the stimulated growth at the early stage of lettuce were performed from the samples of lettuce grown on the pots in the glass house. The analysis of stress-responsiveness in plant and soil is an important route to the discovery of genes conferring stress tolerance and their use in plant science programs. Comparative proteomics of the lettuce leaf have been used to identify the specific tissue-expressed proteins. These lettuce tissue samples have the different illite treatments. Protein extracts were first prepared from the illite-treated lettuce samples and the proteins were separated by two-dimensional electrophoresis (2-DE) and visualized by staining with Silver, and gel images were analyzed with a computer assisted image analyzer. After the visual comparison, the protein spots that were differentially expressed in the applied lettuce tissues were cut from gels and analyzed by liquid chromatography matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (LC-MALDI-TOF-TOF) and peptide mass fingerprint database searching. Then, proteome in the illite-treated and untreated spots were compared. As a results, three proteins in the illite-treated spots were selected and identified as follows: one protein, RuBisCO small subunit [Lactuca sativa] in the powder illite-treated spots; two proteins, Plastidic aldolase NPALDPI [Nicotiana paniculata]and Putative ABC transporter periplasmic sugar-binding protein in the particulate illite-treated spots. Whereas, some minor proteins in the untreated spots were also expressed.