Teachers often see science as an important subject to teach, but they are often reluctant to teach science because they feel inadequately prepared or are unsure of their abilities (Atwater, Gardener, and Knight 1991; Bybee 1991; Dickinson et al. 1997). While this is very discouraging, at least practicing teachers recognize that they have a deficiency in science content knowledge. This is a dilemma that is faced by many teacher-training programs. But, if it is our goal to develop citizens who understand basic science concepts, then should we not expect teachers to already have a good general science background? This article discusses the necessity of science content knowledge.