Based on the classical definition of an industrial hygienist, it is obvious that a certain level of competence in health physics aspects is required. The converse may also be true. Individuals in both professional organizations are urging more interfacing between the two groups. In light of this, the author presents a matrix which illustrates the progressive steps involved in ionizing radiation hazard judgment, based on the classical industrial hygiene definition. The author then presents his opinion (using examples from literature and his own experience) as to the delineation of areas in which a certified hygienist should be able to handle potential ionizing radiation hazards successfully. It is stressed that the hygienist must, in addition, be able to know when to consult a qualified health physicist in situations which require a more advanced level of expertise.