Therapeutic equivalency among different drug products is one of the major issues confronting many clinicians today who are functioning as members of pharmacy and therapeutic committees and state Medicaid programs (SMP). Selection of one of the available slow-release potassium chloride formulations for inclusion in a hospital formulary or SMP exemplifies one of these therapeutic equivalency issues. To evaluate this issue, we studied 20 hypertensive adult patients receiving hydrochlorothiazide 50 mg/d to determine if there are significant differences between the administration of 24 mEq of Slow-K given as 8 mEq/tablet tid, and 30 mEq of K-Tab given as a 10 mEq/tablet tid. The study was conducted in a randomized, open-label, crossover design in which the two drug formulations of potassium chloride were compared over two four-week treatment periods. Results from this study indicate that 24 mEq of Slow-K and 30 mEq of K-Tab were equally effective in maintaining serum electrolyte concentrations, blood pressure measurements, and electrocardiogram evaluations within normal limits in all 20 hypertensive patients studied. Furthermore, no adverse effects were noted with either potassium chloride formulation, and patient acceptance, tolerability, and compliance to prescribed dosing regimens were similar for both products. Based on our findings, therefore, we conclude that 24 mEq of Slow-K and 30 mEq of K-Tab given three times daily as 8 mEq and 10 mEq tablets, respectively, are therapeutically equivalent.