The author, based upon his experience with drugs and a partial review of recent literature, makes a critical evaluation of ten phenothiazinic compounds. He remarks the fact that these compounds must be studied from the viewpoint of its therapeutical and toxic effects. The author's conclusions are: 1. The phenothiazine compounds can be characterized by their chemical estructure; 2. The compounds with a lateral chain of three carbons are the most efficient. The presence of a piperil radical, and a chloride or fluoride increases the potency and side effects; 3. None of the studied compounds is entirely without side effects; 4. The therapeutic effects are equivalent, when the compounds are used in proportional dosages; 5. Among the compounds, promazine and levopromazine are the ones that combine the best therapeutic effect with the less incidence of side effects.