Research on stereoscopic image and video processing has been the new trend in the recent years. Measurement of visual quality is of fundamental importance for numerous stereoscopic image and video processing applications. The goal of quality assessment is to automatically assess the quality of images or videos in agreement with human quality judgments and optimize the stereoscopic image or video systems. Unfortunately, human are lack of the knowledge for the perception quality of stereoscopic images. In this paper, we present experimental results of an extensive subjective quality assessment experiment for stereoscopic images in which a total 400 distorted stereoscopic images were evaluated by about twenty human subjects. The stereoscopic images quality data obtained from 8,000 individual human quality judgments is used to build a database that can be exploited for understanding perception of stereoscopic images and provide data for objective assessment metrics designing. The experimental results indicated that the quality perception of the distorted stereoscopic images is content and distortion types dependent.