Exposure to phobic stimuli in subjects with specific phobia typically results in increased anxiety, ranging from mild to severe, followed by gradual habituation. The Internet is a candidate medium for the delivery of phobic stimuli to phobic subjects, such as pictures, video clips or computer animations. Delivery of such images in home settings warrants careful attention to the range and time course of anxiety responses elicited, and to tailoring of progression through hierarchies of images. The agency of the user is paramount, they need to have the final say at all stages of exposure as to whether to proceed or not. We have incorporated solutions to these requirements in the design of an internet-based exposure program (FEARDROP). This employs a database repository of pictures and videos of phobic stimuli. Images are called up by the user engaging a tracking circle with their mouse and following it around the screen. The image fades out if the circle is not followed, a form of 'dead man's brake'. Anxiety responses are measured at intervals on a visual analogue scale and graphed for the user. Initial results show substantial habituation to spider pictures within minutes, with a controlled comparison to video images in progress.