This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

1. To determine the effect of spironolactone as monotherapy on:

   1. Mortality

   2. Morbidity

   3. Systolic and diastolic blood pressure compared to placebo in adults (of varying age and race) with essential hypertension (with and without co‐morbidities).

2. To determine whether spironolactone is associated with an increased incidence of adverse effects compared to placebo.