The most common non-malignant, age-related disease in men is the benign prostatic hyperplasia (BPH). Androgens and genetic predisposition play important roles in normal prostate growth and in BPH progression. However, accumulating evidence indicates that factors such as aging and obesity also can contribute to the BPH etiology. Management of BPH includes medical treatment or surgery. Currently, the drug therapy uses the alpha1-blockers and/or inhibitors of the 5-alpha reductase enzyme (5ARIs). Latest studies demonstrated that a fraction of patients (up to 30 %) are resistant to this therapy. This article reviews the new risk factors in BPH etiology as well as the mechanisms of resistance to 5ARI therapy.