This research case describes the use of parafoveal subliminal priming. The theoretical background is briefly described and focuses on gender differences in the jealousy-evoking effect of a rival’s characteristics. The experiment described here was aimed at detecting whether participants were influenced by a romantic rival’s clothing style when it was presented outside their conscious awareness. The method we employed was parafoveal subliminal priming, which consists of extremely brief presentations of stimuli in one of the four parafoveal regions of the visual field (the corners of the computer screen). After detailing the basic principles of this procedure and the procedure that was followed in the current research case, the remainder of the text focuses on the decisions that were made with respect to the method and the procedure: the stimulus materials, the use of parafoveal priming, and the use of a cover story. Each decision includes a lesson that was learned from the outcome of the decision, and each decision includes suggestions for changes to the current design, procedure, or materials to improve future research.