New astronomical science will be enabled by the use of array technology in radio astronomy. Development efforts concentrate on two concepts: aperture arrays and phased array feeds. Key challenges in the front-end development of such systems are the bandwidth, low-noise and stability requirements. A (dense) phased array feed prototype in a 25 m dish of the Westerbork Synthesis Radio Telescope (WSRT) successfully demonstrated the ability to electronically scan the beam about 2 half-power beamwidths in both directions while retaining a high antenna efficiency and low system noise temperature. The final system will lead to a 20× improvement of the WSRT survey speed. The Low Frequency Array (LOFAR) operates in the 15 – 240 MHz band using sparse antenna arrays. The Low-Band Antenna stations (15 – 80 MHz) have a pseudo-random configuration of the antenna elements to smoothen the station beams. Both aperture array and phased array feed technologies are important pathfinders for the next generation radio telescope, the Square Kilometre Array.