How would you feel about your husband, wife, or partner masturbating using pornography or erotica? For many, this would be a betrayal – a kind of cheating. I explore whether monogamous relationships should forbid solo masturbation using erotica and pornography, considering two possible objections: (1) the objection that such activity is a kind of infidelity; (2) the objection that such activity involves attitudes, usually attitudes towards women that are incompatible with an equal, loving relationship. I argue that the use of (...) erotic material in solo masturbation should not count as cheating. Solo use of pornography differs significantly from interpersonal sexual activity. Thus, unlike causal interpersonal sex, it does not undermine the role of sex within the relationship. Additionally, freedom to explore sexual fantasy through masturbation is an important element of sexual autonomy. Objection (2) holds against some but not all erotic material. Sexual enjoyment of pornography that depicts, or is produced by, suffering or degradation involves a way of seeing others that has implications for the user’s relationships with others, particularly sexual relationships. However, not all erotic material involves objectionable attitudes towards others. Thus partners should allow moderate use of some types of erotica in solo-masturbation. (shrink)