Day-of-week variations in O_3, NO_x, CO and PM_(10) were analysed in the southwestern region of Europe (specifically Andalusia, Spain) using hourly concentrations collected at 43 stations (representing five typologies) over 6 years (2003-2008). This area has air pollution problems, and the study of the weekend effect is used as a tool to plan future strategies for emissions reductions. Maximum daily 8 h averages for O_3, daily 90^(th) percentiles for NO, NO_2 and PM_(10) and mean daily values for CO were calculated and used to assess the weekend effect by applying three different metrics: weekly evolution, weekend-weekday differences and average daily difference between weekends minus workdays. Based on daily parameters and weekend-weekday differences, all the measured air pollutants exhibited clearly reduced concentrations (oscillating between 25 to 85%) on weekends, mainly at urban and suburban stations, with the exception of O_3 (less than 10 μg/m^3). This decrease on weekend days was mostly observed for NO, NO_2 and PM_(10) at urban stations, while differences at industrial and rural stations were low or null. CO showed a low reduction. Using the daily cycle of differences (weekend minus workdays) as a reference, positive deviations were observed at night and negative differences were observed during the daytime for NO, NO_2 and PM_(10) at urban traffic, urban background and suburban background sites. A reduction in morning rush hour traffic during the weekends was reflected in the data from urban stations, which showed a decrease of up to 50, 15 and 12 μg/m^3 for NO, NO_2 and PM_(10), respectively. An opposite daily behaviour was found for ozone, which showed an increase at urban area sites of up to 15 μg/m^3 in the early morning.