Recently, Rotondi (1967) found that 5s' self-classification (which also agreed with measured fluctuations in oral temperature) as morning-active (MA) or evening-active (EA) interacted with the time of day at which they were tested in determining mood scores on the Gough Adjective Check List (ACL). He interpreted his resulrs in terms of a dimension of social desirability, i.e., MA Ss presented a more socially desirable picture of themselves on the ACL in the morning and EA Ss in the evening. His results were consistent with literature, suggesting that cyclical changes in mood, alertness, and efficiency during wakefulness are correlated with physiological indices (Kleitman, 1963). Thayer (1967) has developed a self-report instrument measuring transient levels o f activation, the Activation-Deactivation Adjective Check List (AD-ACL). A General Activation (GA) factor was found in three physiological validation studies to be the most sensitive measure of transient levels of activation. Ss in the present preliminary study were 20 MA males and 21 EA males selected from college classes on the basis of Rotondi's questionnaire. The Marlowe-Crowne Social Desirability (M-C SD) Scale (Crowne & Marlowe, 1964) was administered to 1 1 MA Ss and 10 EA Ss in the morning and to the remainder in the evening. Ss were retested with the scale 3 wk. later at che opposite time of day. Six MA Ss and 5 EA Ss were administered the AD-ACL during the initial morning testing session and 5 MA 5s and 6 EA Ss were administered the AD-ACL during the initial evening testing session. A t for correlated samples showed the mean M-C SD Scale score (14.05) for the MA Ss tested in the morning was significantly higher than the mean score (12.00) for these MA Ss tested in the evening (P < .05, one-tailed). The mean score (12.33) for EA Ss tested in the evening was not significantly different from the mean score (13.42) for EA Ss tested in the morning. A t for non-correlated samples showed that MA Ss tested in the morning had a significantly higher group mean GA factor score (19.20) on the AD-ACL than did the MA Ss (13.80) tested in the evening ( P < .05, one-tailed). EA Ss tested in the evening had a significantly higher group mean GA factor score (18.50) than did EA Ss (11.60) tested in the morning ( P < .025, one-tailed). AD-AW results suggest a possible relationship between an individual's self-classification as morning or evening active on Rotondi's questionnaire and physiological correlates of activarion. However, Rotondi's explanation of his results in terms of social desirabilicy was only partially verified (i.e., for MA Ss). Possibly, the difference berween the two studies reflects a difference between the Gough ACL, which has Ss describe how they feel at the moment, and the M-C SD Scale, which asks Ss to describe habitual response patterns. It seems plausible that the former self-description might be more consistently related to momentary activation level than the latter. REFERENCES CROWNE, D. P., & MARLOWE, D. The approval motive: studies in evaluative dependence. New York: Wiley, 1964. KLEITMAN, N. Sleep and wakefulness. Chicago: Univer. of Chicago Press, 1963. ROTONDI. J. M. Mood as a function of time of day in morning-active and eveningactive persons. Unpublished MA thesis, Univer. of Wyoming, 1967. THAYER, R. E. Measurement of activation through self-report. Psychological Reports, 1967, 20, 663-678. (Monogr. Suppl. 1-V20) Accepted March 20, 1970.