Novel furobenzisoxazole derivatives of the formula (I): ##STR1## (wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 which may be the same or different represent a hydrogen atom, a halogen atom, or a lower alkyl group having 1-4 carbon atoms; R.sub.5 is a hydroxymethyl group, a carboxyl group or a lower alkoxy carbonyl group having 1-3 carbon atoms; and X is a sulfur atom or a --CH.dbd.CH-- group), as well as intoxic salts thereof when R.sub.5 is a carboxyl group, and process for preparing the same are disclosed.The derivatives of formula (I) and nontoxic salts thereof have hypotensive, uricosuric and diuretic activities and hence ae useful as therapeutics for treating hyperuricemia, edema and hypertension.