Clinical efficiency of course treatment has been assessed for 5 long-acting drugs of theophylline series: retaphylline (Finland), theo-dur (Sweden), durophylline (Yugoslavia), theopek and theobilong (USSR). The drugs were tested in 139 patients with chronic++ bronchial obstruction. It was established that first-line therapy with theophylline should be started with low doses (400 mg/day) and last for 3 days to define individual sensitivity to theophylline drugs followed by increasing doses. On day 7 serum theophylline levels were to be measured for control and dose correction. In cross administration and adequate doses the drugs activity was similar. For patients suffering from nocturnal asthma attacks it was an atypical doze regimen implying administration of two-thirds of the day, dose in the evening that produced the highest effect. The incidence and severity of CNS, cardiovascular and gastrointestinal side effects varied with the dose blood concentration and individual sensitivity to theophylline.