A measure of young children's generalized tendency to expect positive or negative outcomes (Optimism-Pessimism Test Instrument : OPTI) is described. Descriptive data and evidence for the measure's reliability for first- and second-grade children are provided. Validity is assessed by the measure's relationship to several other measures of personality constructs. Moderate but significant correlations were found between OPTI and attitude toward school, self-concept, delay of gratification, and locus of control. These significant correlations suggest that the meaning of such personality dimensions may be clarified by further examination of their relationship to a generalized expectancy for positive or negative outcomes. The OPTI measure could be a useful research tool in such investigations.