The purpose of this study is to a) explore connections among number sense, mental computation performance and the written computation performance of elementary preservice school teachers; and b) explore the correlation among mental computation skills, computation skills, effect issues and number sense. The sample was composed of students in six intact entry-level mathematics sections of a course populated by preservice elementary school teachers. One hundred fifty-five participants from these six classes completed data collection tasks during the Spring 2002 semester for the study. Regression analyses were used to investigate the correlation of written computation skills, mental computation skills, and affective domain with regard to number sense. Three of these subscales of Conference Learning Mathematics, Mathematics Anxiety, Effectance Motivation of Mathematics, Mental Computation Test score, and Written Computation Test score were found to positive significantly correlate with Number Sense Test score success at the a = 0.001 level. Overall, the six independent variables considered in this study accounted for 57.1% of the variation in Number Sense Test score, with Mental Computation Test, and Written Computation Test having the strongest effects.