The paper describes the theoretical and experimental basis of lithium action, tremor as the main side effect, and the attempt of treating tremor in Parkinson’s disease by administration of β-receptor blockers. A review is presented of β-receptor and propanolol action, as well as its relation to lithium-induced tremor. 15 of own cases, 10 of which were affected by lithium-induced tremor and the other 5 by psychogenic tremor, were treated by 2 X 40 mg (or 4 X 20 mg) propanolol over a period of 7-28 days under permanent supervision of lithium blood level. The ten lithium-treated patients belong to the following diagnostic groups: manic-depressive psychosis, endogenous depression, ‘vitalised’ neurotic depression and schizo-affective psychosis. Out of the 8 positive results obtained, 3 were satisfactory and 5 excellent. No side effects were observed. Tremor modifications were objectivated by writing and drawing tests. Further possibilities for more detailed studies are discussed.