Twenty non-treatment-seeking methamphetamine-dependent volunteers will complete procedures during treatment with placebo and study medication, in random order, using a within-subjects, double-blind, placebo-controlled design. There will be a two week period between each phase. The dose of doxazosin needed to alter the effects of methamphetamine is unknown and preclinical animal studies have not been conducted. Because of this, initially the investigators will study the effects of a low dose of doxazosin (4mg daily) compared to placebo daily. Methamphetamine (0, 10, and 30mg, smoked) will be administered during treatment with 4mg doxazosin/placebo. Methamphetamine will be administered in ascending dose (10mg followed by 20mg) with the 0mg dose randomly interspersed to maintain the blind. Cardiovascular measures and subjective effects ratings will be assessed following methamphetamine administration.