A new computerized instrument (the Multimedia Behavioral Avoidance Test, or MBAT) for blood-injury-injection phobia (BII) assessment is presented. Analogous stimuli such as images and videos can also elicit anxiety responses; thus, they can be used for the assessment of phobia. The MBAT was applied to participants via computer, and subjective anxiety responses and time latency were recorded. The MBAT was composed of 30 original images and 30 videos related to blood, injury and injections. The MBAT was compared with other pencil-and-paper questionnaires for BII phobia, and heart rate was also measured with a pulsioximeter. The participants included 160 students and professionals (34.5% males, 65.6% females; mean 28.6 years old). The results showed a high reliability for internal consistency in images and videos (α = .98 both), with a single factor that groups all the items. In addition, the MBAT had high concurrent validity (r = .78 to .85) with the different anxiety scales compared. The MBAT diagnosed 12 participants with possible BII phobia. It is a useful instrument in the assessment of this kind of phobia because it is easier and quicker than pencil-and-paper questionnaires, it uses more objective measurements, and it is useful in planning subsequent exposure with images and videos.