Triplet Higgs bosons at $e^+e^-$ colliders
  We investigate the possibility of probing the triplet Higgs boson sector via single charged Higgs production in the process $e^+ e^- \to H^+ l \nu_l$, at high energy electron-positron colliders, using the tree level $H^+W^-Z$ coupling which is a unique feature of such models. We find that even LEP-200 can give nontrivial information upto $M_{H^{\pm}} \simeq 120 $ GeV if the doublet -triplet mixing is not restricted by the current value of the $\rho$ parameter which is the case in models with a custodial symmetry. Further we point out that in such models, the 4-body, tree level decay $H^+ \to W^*Z^* \to 4$ fermions dominates and hence provides a very clean signal when the four fermions are leptons. At NLC the discovery range for the charged Higgs in triplet models via this process is $\sim 400$ GeV. 
R.M. Godbole, B. Mukhopadhyaya and M. Nowakowski