Although some lies can damage relationships, we hypothesized that altruistic white lies (i.e., lies of minimal importance told to protect another) may benefit romantic relationships by buffering individuals against the potentially damaging effects of hurtful, albeit relatively minor, information. Positive relationship illusions (e.g., believing your relationship is more immune than others’ relationships to conflict and divorce) have been shown to be positively associated with relationship satisfaction. We hypothesized that altruistic white lies may help create positive illusions within relationships. In order to evaluate the potential links between altruistic white lies, positive relationship illusions, and relationship satisfaction, we created and validated a new scale called the Lying In Amorous Relationships Scale (LIARS). This scale assesses individual differences in attitudes toward telling altruistically motivated white lies to a romantic relationship partner. In a series of three studies we assessed the factor structure, internal consistency, test-retest reliability, and construct validity of the LIARS, as well as whether favorable attitudes toward altruistic white lies are positively correlated with positive illusions and relationship satisfaction. The results of Study 1 indicated that the LIARS is a reliable, unidimensional scale that is best conceptualized as a single factor. In Study 2 the LIARS demonstrated good discriminant validity with measures of academic achievement and locus of control, as well as good predictive validity with behavioral intentions to tell one’s partner an altruistic white lie in response to a variety of scenarios. As predicted, LIARS scores also differed as a function of participants’ marital status and affiliation with the university. Contrary to predictions, the LIARS scores of men and women did not differ. Additionally, the LIARS did not demonstrate convergent validity with measures of empathic concern and perspective taking. Study 3 indicated that, contrary to our predictions, LIARS scores were negatively, rather than positively, correlated with positive relationship illusions (r = -.22) and relationship satisfaction (r = -.36). Thus, more positive attitudes toward telling altruistic white lies to a relationship partner were associated with fewer positive illusions and less relationship satisfaction. Stated another way, a preference for truth-telling (versus telling white lies) was associated with more positive illusions and greater relationship satisfaction. Overall, we conclude that the LIARS is a reliable measure of individual differences in attitudes toward telling one’s partner altruistically motivated white lies that demonstrates good discriminant and predictive validity. We also conclude that a preference for telling one’s partner the harsh truth (as opposed to telling altruistic white lies) is associated with greater positive illusions and relationship satisfaction, particularly for younger individuals, presumably with less relationship experience.