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The role of excitonic excitations in wide-gap II-VI and nitride semiconductors is reviewed with focus on the recent research at Bremen University. More-particle excitations such as trions and biexcitons are studied including their contributions to nonlinearities in the coherent regime and to lasing. Specific questions concerning laser processes in wide-gap materials are addressed. IntroductionWide-gap semiconductors such as most of the Zn and Cd based II-VIs or the nitride based blue to UV emitters are model materials for exciton and Coulomb correlation effects on the whole time and a large intensity scale since excitons in these compounds are much more stable as in conventional III-V semiconductors widely used for optoelectronic applications so far. This in particular holds for lower-dimensional structures exhibiting exciton binding energies exceeding those of the optical phonons. Thus, even at high electron-hole densities and rather elevated temperatures, lasing is still strongly governed by Coulomb correlation effects [1,2], what makes wide-gap materials rather different from III-Vs concerning this important aspect of application. Also with respect to very basic phenomena such as higher-order contributions to coherent multi-wave mixing, or propagation effects, the role of exciton correlation is extremely significant [3][4][5][6][7]. This paper is a short review of the recent activities of the Bremen group in the above-mentioned fields.