Abstract Thirty-one 1, 3, 7, 8-substituted xanthine derivatives have been synthesized and evaluated for bronchodilator and antibronchoconstrictory activities in in vitro tracheal relaxation and in vivo bronchospasm inhibition models. Activity tests have been complemented with phosphodiesterase inhibition and toxicological data. Structure-activity relationships are discussed. Compound 21 (1, 3-diisobutyl-8-methylxanthine) has been ...