Among methodological concerns specific to code-switching (CS) research is the design of the target stimuli used in experiments with an acceptability judgment task. We argue here that research which makes use of CS data of this type must also incorporate monolingual stimuli into the experimental design, specifically monolingual stimuli judged by the same bilingual participants who judge the code-switched stimuli. We do so by reviewing two sets of experimental CS data we collected and exploring the role that monolingual stimuli can play in the analysis of that data. In each experiment, an analysis based solely on acceptability judgments of the CS stimuli leads to one interpretation, while incorporation of results from the monolingual stimuli leads to a distinct interpretation. We show that it is the interpretation integrating the monolingual acceptability judgments which is more valid, thereby arguing for the value of monolingual stimuli in design and analysis.