The authors report on the results of treatment of threatening premature labour with clenbuterol. The daily dose was 40 micrograms twice and later 20 micrograms twice with good efficiency. Action of clenbuterol relating to tocolysis, metabolism and cardiovascular system has been compared with fenoterol-perlongettes. 61 pregnant patients were randomized by computer in two groups, 32 ones having clenbuterol tablets and 29 ones having fenoterol perlongettes. No electrocardiographic changes could be demonstrated with clenbuterol, but extrasystolic episodes have to be observed in two following fenoterol-perlongettes. No intravenous treatment is necessary using clenbuterol tablets. Therefore cardiac overload caused by liquid supply may be prevented, simultaneously the peril of pulmonary edema can be diminished. In our opinion tocolysis with clenbuterol tablets is a successful method of treatment of premature labor.