We tested the prediction that resting frontal brain asymmetry would be a marker of vulnerability for depression among adolescents. Baseline electroencephalographic (EEG) activity was recorded from 12 to 14-year-old adolescents whose mothers had a history of depression (high risk group) and whose mothers were lifetime-free of axis I psychopathology (low risk group). High risk adolescents demonstrated the hypothesized pattern of relative left frontal hypo-activity on alpha-band measures. Such effects were specific to the mid-frontal region and generally consistent across reference montages. Socio-economic status (SES) also predicted alpha asymmetry. When the effects of SES and risk status were jointly assessed, SES contributed unique variance to the prediction of frontal brain asymmetry. The implications of the observed relations among maternal depression, SES, and frontal brain asymmetry are discussed.