The study involved a total of three hundred (300) subjects; 100 women aged 17-40 years, 50 women aged 17-40 years, 50 women aged 55-68 years, 50 men aged 17-45 years, and 50 men aged 55-70 years. The reference ranges for some reproductive hormones (Prolactin, FSH, LH and testosterone) were determined using the enzyme-immunoassay method. The values were compared with previously existing values, which were obtained by radio immunoassay method. The results indicated that for the polypeptide hormones (Prolactin, LH and FSH), the enzyme immunoassay method gave lower values and narrower ranges than radio immunoassay. On the other hand, the enzyme immunoassay method gave higher values and wider ranges for the steroid hormone,(testosterone), than the radioimmunoassay method. These differences are due to differences in assay standards and design. Hence, replacing the traditional radioimmunoassay with enzymeimmunoassay, since the enzymeimmunoassay is cheaper and more accessible, will unavoidably cause some analytical shifts and affect the interprettation of the results of endocrine investigation in reproductive medicine.