Breakthrough pain is a transitory exacerbation of pain that occurs in addition to otherwise stable persistent pain. The wide differences in estimation of incidence reported in literature are probably because of different settings and meanings attributed to the definition of breakthrough pain. European countries prefer to use the term of episodic, which seems to be more meaningful in the different languages. A specific assessment and precise pain characterization are essential to plan the most appropriate treatments, as the approach can be completely different. Control of persistent pain is essential to screen and distinguish the episodes of pain flares from situations of uncontrolled pain, unmasked by frequent episodes of pain. A relation between transient pain and baseline regimen has been found. Despite the relevance of this temporal pain pattern for the influence on the outcome and quality of life, few controlled studies have reported the possible efficacy of different drugs, route of administration and modalities of administration in different circumstances.