This paper presents results of monitoring of benzene and its alkyl derivatives (BTX) in ambient air. The measurements were performed in zabrze, using an automatic analyzer. Concentrations of BTX from August-September 2001 and August-September 2005 were compared. The experiment of comparison was done to assess effects on air quality of the coking installation shutting down. The mean concentration of BTX significantly dropped. In general, neither the character of diurnal distribution of BTX concentrations nor the concentration maxima changed. Instead, in 2005, the share of low concentrations was greater and high BTX episodes were less frequent.