Noncarious cervical lesions have a multifactorial etiology. Mechanical stress has been identified as one of the factors, but little evidence exists for its cause-effect relationship. This study was conducted at three different pH levels to observe the surface loss on dentin beams under tension and compression. Bovine dentin beams (10 x 3.75 x 1.45 mm) were fixed at one end and immersed in 0.1 M lactic acid solution at pH levels 4.5 (n = 20), 7 (n = 20), and 10 (n = 20) for 5 days under a load of 6.5 N (663 g). The mean surface loss was more on the surface under compression than that under tension at pH 4.5 and pH 7 than at pH 10. Also, the surface loss on the beams decreased as the distance from the fixed end increased. It was concluded that stress and lower pH both increase surface loss at the fixed end of the beam, which in a tooth represents the cervical region.