In this study a simple correlation is developed to predict monthly average daily global solar radiation on a horizontal surfaces for different Iraqi locations. For fiveyears interval (1981-1985), monthly average daily global solar radiation and sunshine duration data were measured on horizontal surfaces at some Iraqi cities (Kirkuk,
Baghdad, Nasiriyah). A mathematical linear correlation represented by (Angstrom correlation) was applied to estimate the global radiation from hours of sunshine duration for these cities at the specified day of each month as shown in tables (2a, b, c). The model was compared with three different mathematical correlations models (quadratic, logarithmic, and exponential) to get the best fit among them. The obtained models have a high value of regression coefficient and give best fit through the measured values. In this study, the monthly average daily diffuse and beam radiations on horizontal surface were estimated from the measured global radiation. The overall
results show that, Baghdad city received higher radiation on the horizontal surface than Kirkuk and Nasiriyah.