In this paper, we present a new micro fiber optic probe for in-vivo diffuse reflectance measurements of human epithelial tissues. The probe consists of seven, 120times120 mum collection fibers and one 200 mum incidence source fiber, arranged into a side-viewing configuration by using curved air-core waveguides with high optical transmittance. The outer dimension of the probe is 2times8 mm2. The extremely small size, high transmission efficiency and side-viewing capability of the new probe make it suitable for endoscopic spectroscopic applications inside the human body.