The antihypertensive effects fo aldactazide and serum electrolytes changes before and after treatment with aldactazide were observed. The followings were obtained: 1. Results of antihypertensive therapy with aldactazide in 23 hypertensive patients revealed good effects in 52.17%, fair in 26.09%, poor in 8.7%, and failure in 13.04% of cases. In 78.26% of cases, good or fair control of blood pressure was obtained. 2. Daily doses of aldactazide ranged from 25mg to 50mg depending upon the level of blood pressure. The antihypertensive effects were appeared after average 11 days of administration. 3. The side effects during treatment with aldactazide were dizziness, weakness, indigestion, headache, and restlessness in 26.28% of cases (6 of 23 cases). 4. No significant changes in serum Na and K values were observed before and after treatment with aldactazide for average 23 days.