Aims: To assess the influence of occlusal stabilization splints on sleep-related respiratory variables in obstructive sleep apnea (OSA) patients. Methods: Ten OSA patients (47.3 ± 11.7 years of age) received a stabilization splint in the maxilla. All patients underwent three polysomnographic recordings with their splint in situ, and three recordings without their splint in situ, using a randomized crossover design. Results: Repeated-measures ANOVAs did not yield statistically significant differences in the Apnea-Hypopnea Index (AHI) or in the Epworth Sleepiness Scale (ESS), neither between the three nights without the stabilization splint (AHI: F = 2.757, P = .090; ESS: F = 0.153, P = .860) nor between the nights with the splint in situ (AHI: F = 0.815, P = .458; ESS: F = 0.231, P =. 796). However, independent ANOVAs revealed that the mean AHI of the three nights with the stabilization splint in situ (17.4 ± 7.0 events/ hour) was significantly higher than that of the nights without the splint in situ (15.9 ± 6.4 events/hour) (F = 7.203, P = .025). The mean increase in AHI with the splint in situ was 1.4 ± 1.7 (95% confidence interval = -1.9-4.7). No difference in ESS was found when both conditions were compared (F = 1.000, P = .343). Conclusion: The use of an occlusal stabilization splint is associated with a risk of aggravation of OSA; however, the effect size was small, which reduces the clinical relevance of the study. Keywords: crossover design, obstructive sleep apnea, occlusal stabilization splint, randomized controlled trial, vertical dimension