A drilling system is presented for use in drilling lateral boreholes from a main borehole. The drilling system generally comprises a drilling machine, a drill string connected to the drilling machine so as to be driveable in an axial direction, and a guide connected to the drilling machine such that when the drill string is driven axially by the drilling machine, it interacts with the guide so as to be directed in a predetermined radial direction. A method of drilling a lateral borehole from a main borehole is also presented, comprising the steps of: positioning the drilling system in the main borehole; anchoring the guide in the borehole; operating the drilling machine to drive the drill string in an axial direction; and deflecting the drill string, by means of the guide, in a radial direction into the wall of the main borehole to drill the lateral borehole.