Raman microspectroscopy was used to study normal, benign and malignant human breast tissues. The Raman spectrum of normal breast tissue recorded with 514.5 nm line of Ar+ laser excitation contains features attributed to carotenoids and lipids. The CH2 bending mode near 1447 cm(-1) in normal tissue shifts up to 1454 cm(-1) in diseased tissues (benign and malignant). The band near 1660 cm(-1) in normal tissue is narrow and sharp; whereas the band is broaden in the diseased tissues. In the region of C-H stretching mode, the 2902-/2860-cm(-1) intensity ratio shows differences among normal, benign and malignant breast tissues. The ratio is the smallest in carcinoma tissue. The observed spectra differences may be used to probe breast lesion. The results show that Raman spectroscopic technique may have clinical applications.