Background: Repetitive questions and temper outbursts form part of the behavioural phenotype of Prader-Willi syndrome (PWS). We investigated the phenomenology of temper outbursts in PWS and their relationship with other PWS behavioural characteristics. Method: Four individuals with PWS were observed (5-10 h), during a number of experimental and natural environment challenges, some of which were expected to trigger temper outbursts. Individual behaviours including crying, ignoring, arguing, questioning, stereotypy, frowning and posture changes were recorded and subjected to lag sequential analysis. Results: All participants were significantly more likely to show repetitive questioning before more challenging behaviours such as crying, arguing or ignoring requests. Precursor behaviours such as frowning and stereotypical behaviour were identified in three participants. Conclusions: Temper outbursts in PWS may be associated with other PWS behavioural phenotypic characteristics such as repetitive questions and "stubbornness". A progression of behaviours may lead up to the most challenging temper outburst behaviours. This may have important implications for effective coping strategies.