This is a Phase I, three period, two sequence, single-center, open-label, randomized, crossover study design. Periods I and II consist of the oral administration of either a single dose of theophylline or bambuterol alone, followed by a 7 day wash out interval. Subsequently, Period III consists of the simultaneous administration of both drugs. All subjects are to be confined to the Oslo University Hospital Research Unit throughout all treatment periods [Study Day 1, 7 and 14]. A sufficient number of healthy adult subjects will be consented in order to enroll 20 and complete 16 subjects who complete all three periods. Replacement of subjects is permitted, if necessary.