Azacyclopentane derivatives of structural formula (I) are selective inhibitors of stearoyl-coenzyme A delta-9 desaturase (SCD1) relative to other known stearoyl-coenzyme A desaturases. The compounds of the present invention are useful for the prevention and treatment of conditions related to abnormal lipid synthesis and metabolism, including cardiovascular disease; atherosclerosis; obesity; diabetes; neurological disease; metabolic syndrome; insulin resistance; liver steatosis; and non-alcoholic steatohepatitis. ##STR00001##