Leptonic decays of D are currently searched for in CLEO II and BES who have reported the observation of 15 3.2 events and 3 events, respectively. No observation of leptonic decays of D-mesons has yet been reported, owing to the smaller branching fraction. We may expect approximately 150 D decays from CLEO III by the year 2001. Also E831 will search for such decays. Like COMPASS their technique involves a D-tagging by detection of the from the decay D D . Since the p of the is not measured in their set up, they must employ other techniques to discriminate against backgrounds from semileptonic decays. The rejection powers and remaining backgrounds have not been estimated. Thus, no expected numbers are quoted concerning the achievable precision. The design goals for COMPASS are again a higher statistics by about a factor 10 as compared to CLEO/E831. In addition, the use of a target detector allowing the detection of the decay kink of the charged meson, should lead to a clean sample of such decays. For this field high statistics is only part of the requirements, the other being a clean identification of the decay topology. Both conditions could also be fulfilled at a /charm factory.