Based on the evidence available at this time and using criteria of effectiveness and cost, thiazides are clearly the drug of first choice. Based on the criteria of efficacy, tolerability and convenience, thiazides are equivalent to or better than all other drugs. Therefore, thiazides are the drug of first choice for most uncomplicated hypertensive patients. There will be a proportion of patients (20-25%) where thiazides are proven ineffective or inappropriate. In these patients or in patients requiring more than one drug, other drugs must be substituted or added. These other drugs will be discussed in Therapeutics Letter 8.