A method of rocking a wheeled infant carrier (30) comprises using a rocking device (10) having a pair of discrete units (12,14). Each unit has a ground-engaging base (18a,b) and a platform (16a,b) supported thereon through bearings for movement relative to the base in a first direction. A drive one (12) of the units has a motor in a housing (20) arranged to drive the platform (16a) of the drive unit relative to its base back and forth in said first direction. A first wheel (34) of the carrier (30) is placed on the drive unit and a second wheel (32) on the second, slave unit (14), with the axes of rotation of the wheels being arranged parallel said first direction. The motor is operated to rock that end of the carrier that is supported by those wheels from side to side.