The psychostimulants d-amphetamine and methylphenidate are thought to be the most effective treatment in children, adolescents, and adults with attention deficit-hyperactivity disorder (ADHD) because they potentiate both dopamine (DA) and norepinephrine (NE) at the synaptic cleft. These medications are not free from side effects and controversy. Newer effective and safe treatments are needed. S-Adenosyl-L-methionine (SAM), the active form of methionine, acts as a methyl donor and is involved in many metabolic pathways. It has beta adrenergic and DA receptor agonist activity. We have been using oral SAM in a sample of well-diagnosed adults with ADHD, residual state (RS) in a 4-week open trial to establish SAM effectiveness and safety and in a 9-week, double-blind, placebo-controlled crossover trial. Preliminary data from the open trial reveal that 75 percent (6 out of 8 male) patients improve on it. The 2 who did not improve had not improved on methylphenidate trial. Improvement ranged from moderate to marked, with minimal and transient side effects that did not interfere with functioning.