Anandamide (AEA) belongs to an emerging class of lipid mediators collectively termed "endocannabinoids". This endogenously synthesized compound has been implicated in multiple processes, mainly related to the regulation of cell growth/death. During pregnancy endometrial fibroblast-like stromal cells proliferate and differentiate into decidual cells, forming the decidua. After reaching its maximum development, the decidua undergoes regression, which appears to be associated with apoptosis. In order to study the role of this endocannabinoid in this process, the effects of AEA upon cell viability and cell death in primary rat decidual cell cultures was investigated. The results obtained demonstrated that AEA induces cell death, in a dose-dependent manner which is associated with morphological alterations, such as nuclear condensation, DNA fragmentation and upregulation of caspase-3/7 activities. Moreover, these effects were attenuated by AM251, a selective antagonist for the cannabinoid receptor CB1. High concentrations induced a dramatic effect in cell viability and morphology, though methyl-beta-cyclodextrin (MCD), a membrane cholesterol depletor completely reversed the cytotoxic effect. These findings suggest that AEA in the uterine environment may play an important role in regulating apoptosis through CB1 and thereby modulate decidual stability and regression during pregnancy. However, it cannot be discarded the hypothesis that AEA, in high concentrations, represent a deleterious factor during this complex process.