Screw compressor that at least comprises the following elements: - a compression chamber that is formed by a compression housing in which a pair of meshed helical compressor rotors (4,5) in the form of a screw are rotatably mounted, which have rotor shafts (7,8) that extend along a first axial direction (AA') and a second axial direction (BB') that are parallel to one another; - a drive motor that is provided with a motor chamber formed by a motor housing, in which a motor shaft is rotatably mounted that extends along a third axial direction and that drives at least one of the aforementioned two compressor rotors (4,5), wherein the compression housing and the motor housing are connected to one another to form a compressor housing, wherein the motor chamber and the compression chamber are not sealed off from one another, wherein the screw compressor is a vertical screw compressor whereby the rotor shafts (7,8) of the compressor rotors (4,5) as well as the motor shaft extend along axial directions (AA', BB', CC') that are oblique or transverse to the horizontal plane, wherein the compression housing forms a base or bottom section of the compressor housing, and that the motor housing forms a head or top section of the compressor housing, wherein the compression chamber is provided with an inlet through the walls of the compression housing up to the compression chamber for drawing in air, as well as an outlet for removal of compressed air, wherein the screw compressor is provided with a fluid, with which both the drive motor and the compressor rotors (4,5) are cooled and/or lubricated, wherein the screw compressor is provided with a cooling circuit for cooling both the drive motor and the screw compressor and through which the fluid can flow from the head of the compressor housing to the base of the compressor housing, wherein the compressor rotors (4,5) both have a high pressure end that is supported in the compressor housing by means of one or more outlet bearings (32,33), wherein the compressor rotors (4,5) both have a low pressure end that is supported in the compressor housing by means of one or more inlet bearings, wherein the screw compressor is provided with a lubrication circuit (40, 45), wherein the cooling circuit and the lubrication circuit are connected to a return circuit for the removal of fluid from the outlet in the base of the screw compressor and for returning the removed fluid to the head of the compressor housing, wherein the compression housing and the motor housing are connected directly to one another to form the compressor housing, wherein the cooling circuit consists of cooling channels that are provided in the motor housing and of the compression chamber itself, characterised in that the motor shaft, at the end opposite the driven compressor rotor, is supported in the compressor housing by means of one or more motor bearings, wherein the lubrication circuit (40, 45) comprises a first lubrication circuit which consists of one or more branches of the cooling channels in the motor housing for supplying fluid to the motor bearing or the motor bearings, and of outlet channels for the removal of fluid from the motor bearing or the motor bearings up to the inlet bearings from where the fluid can flow in the compression chamber, wherein the first lubrication circuit lubricates the motor bearing or the motor bearings as well as the inlet bearings, and wherein the lubrication circuit (40, 45) comprises a second lubrication circuit which is provided in the base for lubricating the outlet bearings (32,33) and which consists of one or more supply channels for the supply of the fluid from the compression chamber to the outlet bearings (32,33), as well as one or more outlet channels for the return of the fluid from the outlet bearings (32,33) to the compression chamber, wherein the outlet channels lead to the compression chamber above the entrance of the supply channels. - a compression chamber that is formed by a compression housing in which a pair of meshed helical compressor rotors (4,5) in the form of a screw are rotatably mounted, which have rotor shafts (7,8) that extend along a first axial direction (AA') and a second axial direction (BB') that are parallel to one another; - a drive motor that is provided with a motor chamber formed by a motor housing, in which a motor shaft is rotatably mounted that extends along a third axial direction and that drives at least one of the aforementioned two compressor rotors (4,5),