Concentrations of 14 polycyclic aromatic hydrocarbons (PAH) and 35 polychlorinated biphenyls (PCB) were measured in the surface waters and atmosphere of Superior lake to estimate the direction and magnitude of their fluxes across the air-water interface. Total atmospheric PCB and PAH concentrations were 1.2 and 3.9 ng per m3, respectively. Fugacity gradients, compound-specific equilibrium and mass-transfer parameters were measured. Superior lake was degassing organic contaminants during the summer months. Mean volatilization fluxes of total PCB (19 ng per m2.day) were similar to estimates of gross atmospheric deposition to the lake. This supported the hypothesis of nonequilibrium steady-state PCB exchange across the air-water interface. There is a bibliography of 64 references.