H-3 classification is available to aliens coming to the U.S. as trainees in virtually any field of endeavor. There are many restrictions. The training must not be available in the alien's own country. The alien can only engage in productive employment if incidental and necessary to the training. The training must benefit the alien's career outside the U.S. The documentary requirements are heavy and complex. H-3 petitions almost always provoke a Request for Evidence. Among the currently favored reasons these days for denying H-3 petitions is that the beneficiary "already possesses substantial training and expertise in the proposed field of training." Thus, the mere fact that the training is unavailable in the foreign country at the same level of sophistication can be insufficient, particularly for the California Service Center. Other potential grounds of denial include the likelihood that the particular skill is unlikely to be used outside the U.S. and that the training will result in productive employment within the U.S. beyond that necessary for the training itself. In short, H-3 petitions can be challenging.

H-3 classification can last for a maximum of two years. The U.S. Citizenship and Immigration Services disfavors H-3s changing to another status, such as O-1B, because of the requirement that the training benefit the trainee abroad. However, consulates do not feel themselves so constrained, and are perfectly happy to issue O or P visas to aliens who have just held H-3 status. With the new visa, U.S. Border Control and Protection will admit them without objection.

H-3 training programs are most valuable to larger institutions that can afford to maintain well-regimented and documented training programs, with regular evaluations, and that can use the trainees in performances as part of their training.