Digital-to-analog converters (DACs) with very high conversion rates and bandwidth are of special interest for optical coherent transceiver systems and arbitrary waveform generators. An attractive solution to provide several channels with very high data rates of tens of Gbit/s is to use a high speed serializer. We present a CMOS serializer consisting of a 19 channel 16:1 multiplexer (MUX) for output data rates up to 64 Gbit/s per channel and a low skew clock distribution network.