An actuator for beds, slatted beds or chairs of the type accommodating, in a cabinet, two drive units based on a spindle and a spindle nut configured as an adjustment element, cooperating with an arm of a rotary shaft for a backrest section and a legrest section, respectively, in the bed, the mattress support or the chair. The two spindles are rotational interconnected and are driven by a common reversible electric motor. By having just one motor and one transmissions, as well as no switching mechanism between the two spindles, a simple and inexpensive structure is provided.