Sexual health is an important component of primary care, and optimal sexually transmitted infection (STI) and HIV testing by doctors could help improve sexual health outcomes for men. Currently, little is known about general practitioners' (GPs') assessment of STI and HIV risk, particularly in relation to male patients, and the degree to which current advice can be translated into consistent testing protocols. The aim of the study was to explore STI and HIV testing strategies for men in general practice and opportunities and barriers to more optimal testing. This study used a qualitative, multiple-case methodology, incorporating 17 distinct GP cases, drawing on in-depth, semi-structured interviews, and using thematic analysis. The following themes were identified: sexual health consultations by men in general practice are usually initiated by the patient; GPs appear to have a consistent rationale for their risk assessments in terms of STI testing; the nature of the doctor's interaction with men influences the quality of sexual health services utilisation; optimal sexual health consultations require sufficient time and a recognition of the 'delicacy' of the consultation content for both patient and health practitioner. The stratified testing strategies undertaken by GPs appeared appropriate given the risk profiles of their patients. Constraints to optimal sexual health consultations were identified, including inadequate consultation time, male utilisation of GP consultations, and challenges in discussing sexual health topics within the consultation. Prioritising men's sexual health as a topic in CME may be helpful.