Twenty-three kinds of 7-(2-hydroxy-3-alkylaminopropyl)theophylline (III to XXXV) were prepared by the reaction of amines with 7-(2, 3-epoxypropyl)theophylline (I) or 7-(2-hydroxy-3-chloropropyl)theophylline, prepared from theophylline sodium and epichlorohydrin, and from theophylline and 1-dialkylamino-2, 3-epoxypropane, and also 13 kinds of their acyl derivatives (XXVI to XXXVIII). Similarly, 10 kinds of 1-(2-hydroxy-3-alkylaminopropyl)theobromine (XL to XLIX) and two kinds of 1-(2-benzoyloxy-3-alkylaminopropyl)theobromine (L and LI) were prepared from theobromine. Among these compounds synthesized, 7-(2-benzyloxy-3-diisobutylaminopropyl)theophylline was found to be an excellent coronary artery dilator.