This study questions the evidence that a parity rule is used during the verification of multiplication. Previous studies reported that products are rejected faster when they violate the expected parity, which was attributed to the use of a rule (Krueger, 1986;Lemaire & Fayol, 1995). This experiment tested an alternative explanation of this effect: the familiarity hypothesis. Fifty subjects participated in a verification task with contrasting types of problems (even X even, odd X odd, mixed). Some aspects of our results constitute evidence against the use of the parity rule: False even answers were rejected slowly, even when the two operands were odd. Wesuggest that the odd-even effect in verification of multiplication could not be due to the use of the parity rule, but rather to a familiarity with even numbers (three quarters of products are indeed even).Besides the issues concerning the representation format in which parity information is coded and the way this information is retrieved (Campbell & Clark, 1992;Clark & Campbell, 1991;Dehaene, Bossini, & Giraux, 1993;McCloskey, Aliminosa, & Sokol, 1991;McCloskey, Caramazza, & Basili, 1985), the role of parity in arithmetic has also been studied (Krueger, 1986;Krueger & Hallford, 1984;Lemaire & Fayol, 1995;Lemaire & Reder, 1999). Infact, several studies have proposed that subjects have access and sometimes use parity information without explicit awareness when doing mental calculation. For instance, it seems that in some circumstances, when subjects are verifying simple arithmetic operations (e.g., 2 X 3 = 6 or 2 + 3 = 5), they do not retrieve the result but use a shorthand strategy for checking for the plausibility of the proposed result. Among the cues used for checking that plausibility, its parity has proven to be relevant. It has been found that adults reject a false result more rapidly when its parity is incongruent with the parity of the correct answer (e.g., 2 X 3 = 7) than when it is congruent with it (e.g., 2 X 3 = 8). This incongruence efThis work was supported by the Belgian National Scientific Research Funds (FNRS) and by the Belgian Federal government (I.U.A.P. on temporal control of dynamic tasks situations and the nature of knowledge representation). We thank Marie-Pascale Noel and Agnesa Pillon for their helpful comments on this work. Correspondence should be addressed to A. Lochy,