An arrangement is provided in a milking system for simultaneous milking of a plurality of milking animals, wherein the milking system comprises a plurality of milking positions (P1-P24) and an arrangement for establishing identities of and expected milking times for the milking animals. Each of the milking positions is provided with teat cups, which are attached to the teats of a milking animal and are connected to a source of vacuum to milk the milking animal. The inventive arrangement comprises means (10) for determining a milking position, at which the milking animal having the longest expected milking time is present, based on the established identities and expected milking times; and a device (11, 13, 17; 20) for performing an action with respect to the milking system in response to the determination.