Progesterone and its analogs may exert opposite effects on cell proliferation, apoptosis, and epithelial-mesenchymal transition, leading to higher cell motility and metastasis. Their ultimate effect is determined by a number of factors: the structure and concentration of the steroid, its affinity for various forms of steroid hormone receptors, activation of nongenomic mechanisms, the composition and proportion of different progesterone receptors and sensors, activity of various signaling pathways, the set of transcription factor coregulators, DNA accessibility in chromatin, activity of steroid-metabolizing enzymes, intercellular interactions within tissues, the hormonal status of the body, disease stage, and species-specific features. The review considers the factors that determine the role progestins play in proliferation and apoptosis of human tumor cells of various origins.