According to Rabbinic sources, the menstrual blood is defied by its color, its source from the womb, and especially its period - the vesset. However, the other sectarian schools - the Qumran sectarians, the Samaritans, and the Sadducees - disagreed with this definition of menstrual blood. The author of the Damascus Document (5:6-7) blames the Pharisees in having sexual relations with menstruating women and in not distinguishing correctly (ka-Torah) between the bloods. He probably supposes that the Pharisees declare impure blood as pure. The view of the Samaritans in antiquity is known only from Rabbinic criticism concerning the Samaritan Halakhah. In m. Nidda 4:1 the Rabbis consider the Samaritan women ritually impure since 'they sit on every blood; namely, in the Samaritan Halakhah every blood that women see is presumably menstrual blood. This broad physiological definition of menstrual blood seems close to the view in the Damascus Document. The details and rationale of the Samaritan view may be illuminated by medieval Halakhaic compositions which unanimously reject the Rabbinic concepts of vesset and claim that every blood is to be considered impure. According to m. Nidda 4:2 the status of the Sadducean women in Rabbinic Halakhah is equal to the status of the Samaritan women. Thus, we may conclude that the Sadducees' attitude was quite similar to that of the Samaritans. Since Pharisees and Sadducees shared the Temple rite, their opposing purity regulations might have caused significant problems concerning the purity of the Temple. In any event, we have demonstrated that while the Rabbis held a restricted (or more "accurate") definition of menstrual blood, the Damascus Document, the Samaritans and probably also the Sadducees held a much broader definition. It may be possible to define the Rabbinic attitude as "nominalistic" while their opponents view may be termed "realistic".