An experimental study of the fiber-optic evanescent field absorption sensor based on tapered sensing probe is presented. The influences of numerical aperture, core radius of the fiber and the taper ratio on the sensitivity of the sensor are investigated. Increase in the numerical aperture of the fiber increases the sensitivity of the sensor while the decrease in the core radius increases the sensitivity. In addition, for a given fiber, increase in taper ratio increases the sensitivity. The relationship has been found to be linear.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.