This research is comprised of two studies designed to explore the effects of online discussion forum aggressive messages and Internet cognitive distortion on users' negative affect and aggression. The results of study 1 revealed 69 users could perceive both disgust and hostility feelings toward aggressive messages conducted by the authors, and classify them into three levels: direct aggression, indirect aggression, and disagreement. Study 2 focused on whether three aggressive messages and Internet cognitive distortion had effects on users' negative affect and online aggression. 359 users read one of messages conducted in study 1, and then finished online questionnaires. The results indicated that there were no significant differences in aggression across interaction between aggressive messages and cognitive distortion. However, in users with high cognitive distortion there was significant reported higher aggression than users with low cognitive distortion. Though users could classify the aggressive level of messages and their negative affect be aroused during the treatment, their aggression was not evoked after reading aggressive messages. High cognitive distortion users' aggression and negative affect were triggered without reading aggressive messages. (Contains 4 tables.)