Two experiments examined the role of necessity and sufficiency relationships in conditional reasoning. The results indicated that perceived necessity and sufficiency predicted variability in reasoning performance for four pragmatic relations (permission, obligation, causation, and definition), for both determinant and indeterminant syntactic forms, and for both a conditional arguments and a truth table evaluation task, as well as when the temporal relationship between the antecedent and consequent events was reversed. These data support the general utility of perceived necessity and sufficiency in the interpretation and evaluation of conditional relationships. However, the effects of necessity and sufficiency were smaller for reversed than for forward statements, which suggests that necessity/sufficiency-based interpretations may be more useful for evaluating some types of conditional relations than others. In addition, people were more likely to accept valid rather than invalid arguments, regardless of necessity/sufficiency relations, a finding that suggests that abstract, content-free representations may play a functional role in conditional reasoning.