The potential of visible/near-infrared (Vis/NIR) diffuse transmittance spectroscopy, in combination with a variety of chemometrics techniques, was investigated to examine the feasibility to non-destructively distinguish transgenic tomatoes from non-transgenic tomatoes. One hundred tomatoes inserted with antisense ethylene receptor gene LeETRI and the same number of their parents were scanned in the Vis/NIR regions. Principal component analysis (PCA), soft independent modelling of class analogy (SIMCA) and discriminant partial least squares (DPLS) regression based on PCA scores were applied to classify tomatoes with different genes into two groups. The results show that differences between transgenic and non-transgenic tomatoes do exist and excellent classification can be obtained after optimizing spectral pre-treatment. The correct classifications of the calibration as well as the validation data set for transgenic and non-transgenic tomatoes were 100% using DPLS after second derivative spectral pre-treatment. The results in the present study show that Vis/NIR spectroscopy together with chemometrics techniques could be a rapid tool to be used for differentiating transgenic tomatoes from conventional tomatoes. (C) 2007 Elsevier Ltd. All rights reserved.