O A multi-jet print head for a continuous ink jet printer has its individual ink jets formed electrostatically instead of using a row of individual nozzles. lnk is supplied continuously through a slot in an electrically conducting body or to an elongated edge portion of such a body, while a strong electrostatic field is applied to draw off the ink as an array of parallel cusps. These break up at their tips to form a stream of ink drops which can then be deflected in known manner. The elelectrostatic field preferably has a reinforcing secondary field superimposed on it, which is cyclically varied at a suitable ink drop production frequency to synchronise formation of the ink drops at each of the cusp trips. This enables means for deflecting the drops to be synchronised with the moving drops for consistent deflections and corresponding optimum resolution. The use of a slot or edge portion reduces problems of nozzle clogging inherent in multi-nozzle arrays and the continuous ink flow provides uniform printing conditions along the length of the print head.