Attribution theory suggests that attributional styles may contribute to the motivational and performance deficits frequently observed in depressed and lonely populations. An Attributional Style Assessment Test (ASAT) was created and administered to college students, along with the Beck Depression Inventory and the UCLA Loneliness Scale. Correlational analyses revealed distinct attributional style differences between the more lonely and less lonely people, especially when attributions were assessed for interpersonal failure situations. The more lonely people attributed these failures more than less lonely people to their unchangeable character defects (abilities and personality traits), and less to their changeable behavioral mistakes (effort and strategy selection). Parallel results were obtained when depression was used as the criterion variable. A second study using a modified version of the ASAT with other college students replicated these findings. Results appear to support the theory linking attributional style to motivational and performance deficits in lonely and depressed populations. (Author/NRB)