The present communication highlights aspects on the aetiology, diagnosis and therapy of sexually transmitted infections (STIs) and some allied infections in which sexual transmission is regarded as possible. The aetiology of many genital infections is still unknown or rather, an aetiological relationship between a given agent and a clinical manifestation is in some infections still debated. The paper will discuss some shortcomings in the current surveillance systems for STIs, if these systems exist at all. Thus, the paper considers their value in estimating the extent of the problem on a general population basis. It also focuses on the discrepancy between the current high prevalence of diagnosed cases of some STIs, such as of genital chlamydia infections, and the relatively low number of complications and sequelae presently seen, in contrast to the comparatively high prevalence more commonly reported in the past. Recent discoveries of novel aetiological agents of STIs, including mycoplasmas, may explain a lack of recovery from infections, due to the common use of antibiotic drugs to which these agents have a natural resistance. The observation of a synergistic effect of a commonly used anti-inflammatory drug, which may overcome antifungal resistance in vulvovaginal candidiasis, will also be reviewed. Furthermore, other reflections concern some of the classic STIs, e.g. lymphogranuloma verenerium, syphilis, gonorrhoea, herpes and condyloma.