Can valid predictions of meaningful nontest criteria be made from personality inventones? To counter a prevailing skepticism on this issue positive evidence from large samples is needed. A regression equation for high school grade-point average was developed from California Psychological Inventory scores on 1384 students from 5 schools. A cross-validational coefficient of .56 was obtained on 1371 students from 9 schools, and a cross-cultural coefficient of .39 for 341 students in Italy. Addition of an ability measure raised the 1st correlation to .68, but lowered the cross-cultural coefficient to 53. The predictive equation stressed traits of responsibility and social maturity, capacity for both independent and adaptive achievement, and efficiency in the use of personal resources.