  We summarize the results of two recent searches for flavor-changing neutral
current, lepton-flavor violating, and lepton-number violating decays of D+, Ds,
and D0 mesons (and their antiparticles) into modes containing muons and
electrons. Using data from Fermilab charm hadroproduction experiment E791, we
examined D+ and Ds pi,l,l and K,l,l decay modes and the D0 dilepton decay modes
containing either l+,l-, a rho0, K*0, or phi vector meson, or a non-resonant
pi,pi, K,pi, or K,K pair of pseudoscalar mesons. No evidence for any of these
decays was found. Therefore, we presented branching-fraction upper limits at
90% confidence level for the 51 decay modes examined. Twenty-six of these modes
had no previously reported limits, and eighteen of the remainder were reported
with significant improvements over previously published results.
