The effect of Kr 339, a central cholinolyte, on the symptoms of 20 Parkinsonian patients was investigated using the double-blind crossover test during two stages of treatment, both of which lasted six weeks. There was a statistically significant (P < 0.05–0.01) reduction in the tremor of the extremities, the jaw and the tongue. No significant improvement was detected in the other Parkinsonian symptoms. Dry mouth, fatigue and restlessness were observed in 6 patients during Kr 339 administration. All these patients were simultaneously given other anticholinergic drugs and five of them laevodopa as well. The side effects occurred almost significantly (P < 0.05) more often in the Kr 339 group than in the placebo group. Kr 339 appears to provide some new benefits in the treatment of at least mild and moderate Parkinsonian tremor. The drug can be combined with other anti-Parkinsonian drugs such as laevodopa, anticholinergic drugs and amantadine.