Background: Human prolactin can be determined in human serum or plasma quantitatively by many techniques such as ELISA, RIA, and ELFA (miniVIDAS).Objectives: To estimate the strength of association of total serum prolactin and free serum prolactin values measured by two different methods [RIA and VIDAS]. And to predict the prolactin value measured by RIA corresponding to a given value by VIDAS.Methods: Two technical methods VIDAS and RIA were used in determination of prolactin level in sera of twenty five women with uterine fibroid conducted at two laboratories admitted at Al-Kadhimiya Teaching Hospital during the period January 2008 to April 2009. Total and free serum prolactin was measured by both VIDAS and RIA using their assay kits. Statistical methods of correlation and regression were used to compare between the two methods.Results: The study revealed a highly significant positive correlations between VIDAS and RIA total and free serum prolactin, r=0.999, R2 = 0.998, P<0.001, r=0.998, R2 = 0.997, P< 0.001 respectively. High linear regression equations were found between VIDAS and RIA total and free serum prolactin, y= 0.358x+ 0.57, R2 = 0.998 and y= 0.355x+0.49, R2 = 0.997 respectively. The recovery percentages of prolactin (R %) in two methods were approximately equal to each other, VIDAS R%=50.52±0.89% and RIA R%= 50.38±1.57% respectively.Conclusion: A highly significant positive correlation was found between RIA and VIDAS for both total and free serum prolactin. And high linear regression equations were found between the two methods to predict RIA values corresponding to a given VIDAS value.Keywords: VIDAS prolactin, RIA prolactin, PEG precipitation, macroprolactinemia, uterine fibroid