The results of some crowd behaviour at outdoor music festivals (OMFs) are injuries and sometimes death. The following study has identified a number of factors that are highly likely to have an influence on crowd behaviour and safety at OMFs. The participants in the study (N=44) were specialised security professionals recruited from a single organisation providing security at music based events. These study participants considered problems resulting from intoxication, crowd crushes, the style of live performances and the overall crowd composition as being responsible for the majority of the behavioural concerns they encountered at OMFs. These behavioural factors could form a basic criterion to identify higher risk to patrons at OMFs. Additionally, the study participants considered the overcrowding of venues, a lack of emergency planning and insufficient security staff at events being highly likely to impact on safety at these events. These behavioural and safety factors should be highlighted in pre-event discussions and within the approval processes for OMFs. Highlighting these factors will contribute to the provision of appropriate services and infrastructure based on the specific risk characteristics of each OMF.