This work focuses on the variability of the global solar radiation over the area of Maceio (9 degrees 40'S, 35 degrees 42'W, 127 m), located in Northeastern State of Alagoas, Brazil, during the 1997-1999 period. Solar radiation variability was evaluated on 5 min, hourly, daily, monthly and seasonal scales. The results showed that the maximum values of the hourly global solar irradiation, H-g(h), in the dry (September-February) and rainy (March-August) seasons were 3.18 and 2.50 MJ m(-2), respect ively. The peaks of the hourly average, (H) over bar (h)(g), for both periods were 2.79 MJ m(-2) and the daily average of the global solar irradiation, (H) over bar (g)(d), was 19.89 MJ m(-2). The daily clearness index, K-t(d), was found to be 0.53 (rainy period) and 0.59 (dry period). In clear, partially cloudy (the most frequent) and overcast days, the daily averages of global solar irradiation were 25.20, 19.00 and 8.00 MJ m(-2), respectively. On an annual scale the global solar irradiation changed from 15.00 MJ m- 2 by August to 24.04 MJ m(-2) by November. (c) 2004 Published by Elsevier Ltd.