We have developed a novel transdermal therapeutic system (TTS) which controls the time-lag for drug absorption through the skin. The diffusion coefficient ill the ethylene-vinylacetate (VA) copolymer (EVA) used as a time-lag controlling membrane of a model drug, isosorbide dinitrate (ISDN), is found to be independent of the VA fraction in the EVA membrane. The steady state flux of ISDN through the membrane is unchanged by controlling the fraction of the VA content in the EVA membrane. The in vitro skin permeation experiment shows that the time-lag for drug absorption through the skin can be controlled within the range of 5 to 14 hours. The in vivo skin permeation experiment with repeated application of the device shows that the TTS developed can provide a blood level lower than the therapeutic concentration 6 to 12 hours after the onset of the delivery system. The timed control of blood level obtained in this system is useful to minimize side effects as well as drug tolerance.