Although nasal continuous positive airway pressure (CPAP) is generally effective in correcting sleep-related respiratory disturbance and associated daytime sequelae in obstructive sleep apnea syndrome (OSAS), resistance to and intolerance of CPAP poses a serious limitation to its use. Failure to comply with treatment has been reported to be as high as 25 to 50%, with patients typically abandoning therapy during the first 2 to 4 weeks of treatment. Reasons for discontinuing CPAP therapy have been primarily related to issues of mask discomfort, nasal dryness and congestion, and difficulty adapting to the pressure. Although there has been great variability in the reported rates of CPAP compliance, there have been few systematic studies to evaluate barriers to CPAP compliance or ways to improve compliance. Early identification of CPAP-related tolerance problems or barriers, psychological factors, and the predictive value of pretreatment background variables ( ie, age and gender) may enhance compliance with therapy. An important goal for OSAS management is the development of intervention strategies and educational approaches that minimize side effects and maximize patient compliance. A new classification is presented, along with suggestions and ideas for intervention.