A comprehensive, fully self-consistent, optical-electrical-thermal-gain, three-dimensional model of edge-emitting (EE) nitride diode lasers has been developed and used to simulate a room-temperature (RT) continuous-wave (CW) threshold operation of typical EE designs of a nitride diode laser. With the aid of the model, some RT CW performance characteristics of the laser have been anticipated taking into consideration important features of nitride materials. These features have proved already to be often essentially different from those of other AIIIBV materials, therefore expected properties of nitride devices cannot be estimated on the basis of known properties of analogous devices manufactured from other materials.