In this paper, non-standard types of agreement are examined. Such agreement types are those in which two or more supposedly agreeing categories show discord rather than concord. For example, if a language has noun-adjective agreement, there may, under limited circumstances, be non-standard agreement where the subject is plural and the agreeing adjective is feminine singular. Instances of such agreement discord as found in various languages are investigated. An earlier advanced Syntactic Feature Switching hypothesis which attempted to account for cases of non-standard agreement on the basis of a value changing transformation is examined and rejected. Instead, a principle-derived hypothesis, that of marking, is proposed and defended. Marking, an operation based on markedness and paralleling that of neutralization, shows that non-standard types of agreement are not due to deviations in the agreement transformation or to new power in any other transformation, but rather to an optionality condition (or other conditions) on agreement and a feature-adding transformation which, under certain conditions, "marks" a category. The analyses presented involve the theory of markedness as well as the simplex feature theory, both of which are discussed. (Author)