Sexual stimulation by rubbing against other persons is practised by both men and women, and by adults as well as adolescents. As a regular substitute for sexual relations with a voluntary partner, frotteurism, like voyeurism and masturbation, may be a perversion. Apprehensiveness concerning this undesirable experience is a great cause of social inconvenience for many women wishing to avoid crowds. The presence of frotteurs on public conveyances causes additional use of private automobiles by many to evade this form of indecent assault. Many women workers find superiors leaning over them practising this form of sexual harassment.