The arabino isomer of 3-deazaadenosine was prepared and evaluated for biological activity. It is a mediocre inhibitor of 5-adenosyl-L-homocysteine hydrolase. It was only slightly cytotoxic and slightly inhibitory to the growth of herpes simplex type 1 virus in L929 cells. The title compound, 5, was prepared and found to be a potent diuretic in the rat. At 27 mg/kg, urine output was 250% of the saline control, and the excretion of electrolytes was similar to hydrochlorothiazide control. At 80 mg/kg, the potassium excretion was the same as the saline control, and the sodium and chloride excretions more than doubled. Several analogues were prepared and tested. Some show diuretic activity.