The experience of being in love involves a longing for union with the other, where an important part of this longing is sexual desire. But what is the relation between being in love and sexual desire? To answer this it must first be seen that the expression ‘in love’ normally refers to a personal relationship. This is because to be ‘in love’ is to want to be loved back. This much would be predicted by equity and social exchange theories of interpersonal attraction. Findings suggest however that love differs fundamentally from liking and, consequently, distinct approaches to the theory of love have been developed. A phenomenological theory is then put forward which suggests that the experience of being in love involves a complex of desires for reciprocal vulnerability in order to care and be cared for. Sexual desire is then seen to involve the physical expression of these desires in the form of desires for mutual baring in order to caress and be caressed. Unlike love, however, sexual desire need not refer to the other person's desires. This is supported by the existence of sexual desires like fetishism. It is concluded that other desires which often appear in instances of being in love are not basic to the experience of being in love.