Objective The aim of this report was to raise the issue of the definition and classification of partner terminology in men who have sex with men (MSM) research, particularly in regards to 'fuck buddies'. If definitions in research differ from general consensus in the MSM population, it is possible that public health strategies will be ineffective as the target population may be inaccurate. Methods Thirty semistructured interviews with MSM attending the Melbourne Sexual Health Centre were conducted, focusing on the willingness to change sexual practices to reduce the risk of pharyngeal gonorrhoea. As part of these interviews, men were also asked their views on the terminology they used to describe their relationships and sexual partners. Results The degree of emotional attachment often defined the type or classification of relationships. There was a consensus among men that partners they engaged with for 'sex only' were classified as casual partners and partners with whom there was an emotional attachment or formalisation of the relationship were classified as 'regular partners'. However, the classification of 'fuck buddy' as a regular or casual partner was less clear. Conclusions Further research is needed to ascertain the ways in which men conceptualise sexual relationships and define or classify partner types, particularly 'fuck buddy' relationships. A third category for sexual relationships should be considered to encapsulate fuck buddy relationships.