A discussion of Stephen Krashen's Monitor Theory (1982) of second language acquisition examines five main hypotheses: the acquisition-learning distinction, the natural order hypothesis, the monitor hypothesis, the input hypothesis, and the affective filter hypothesis. Several problematic elements of the theory are pointed out. The discussion supports the basic importance of conscious learning, which is disregarded in the Monitor Theory, and suggests an alternative way to look at language acquisition and learning phenomena from broader perspectives taking into account both skill acquisition theory and human information processing theory. More empirical research needs to be done to identify the developmental stages in second language acquisition and to define the most effective practice at each stage. (Author/MSE)