Article 5(1) of the Convention of 27 September 1968 on Jurisdiction and the Enforcement of Judgments in Civil and Commercial matters, as amended by the Convention of 26 May 1989 on the Accession of the Kingdom of Spain and the Portuguese Republic, must be interpreted as meaning that where, in the performance of a contract of employment, an employee carries out his work in several Contracting States, the place where he habitually carries out his work, within the meaning of that provision, is the place where he has established the effective centre of his working activities. When identifying that place, it is necessary to take into account the fact that the employee spends most of his working time in one of the Contracting States in which he has an office where he organizes his activities for his employer and to which he returns after each business trip abroad.