Time-window sequential analyses test whether a target behavior occurs within a temporal window (e.g., within 2 seconds) after an antecedent behavior more than is expected by chance. This type of question is common when we need to know how one person or event may immediately affect another event or person in the natural environment. Theoretically, the significance of sequential associations from time-window analysis can be tested on the single subject level (Bakeman & Quera, 1995). The present Monte Carlo study was conducted to test the Type I error rates and the difference in sequential associations derived from four methods of time-window sequential analysis. The four methods vary according to whether they analyze the duration of antecedent and target behaviors. The results indicate that time-window sequential analysis method is generally valid. The results were most accurate when antecedent duration and target onset was analyzed. Although analyzing duration of the antecedent did affect the results, the effect size for the difference in results due to presence or absence of measuring duration of the antecedent was extremely small. Time-window analysis results appear unaffected by the decision to analyze the duration of the target event.