Previous research has shown that the level of self-other agreement for personality trait ratings increases with the length of acquaintanceship between the target and the informant. These findings emerge exclusively from studies of well-acquainted pairs in natural relationships and relative strangers interacting in laboratory and classroom settings. The present study examines self-other correlations for trait ratings using the NEO Five Factor Inventory (NEO-FFI; Costa & McCrae, 1992) with 103 pairs of previously unacquainted female college roommates. Assessments were obtained at approximately 2 weeks and again at approximately 15 weeks subsequent to the roommates' initial introduction. Self-other correlations increased for all five NEO-FFI scores and agreement correlations for Conscientiousness were significantly higher than for Extraversion at both occasions. Differences in relationship quality did not moderate self-other agreement for any of the traits. However, better relationship quality was associated with higher other-ratings of Extraversion, Agreeableness, and Conscientiousness and lower other-ratings of Neuroticism after controlling for self-ratings on the same trait. Higher similarity in self-ratings of Neuroticism and Openness was associated with higher self-other agreement for these ratings, and similarity in Conscientiousness was associated with higher relationship quality. These results are considered in light of existing theories of differential trait observability and the effects of unique contexts on trait perception.