The objectives of the present pilot study were to investigate the effect of an oral methionine load on plasma homocysteine in healthy subjects southern Iran. We studied 50 peoples (10 men, 40 women, median age 27.5, range 20-37) referred to screening center for marriage since different part of southern Iran. Methionine (0.1 g kg(-1) b.wt.) was immediately administrated orally in 200 mL of orange juice and a second blood was obtained 4 h later. Plasma level of homocysteine was carried out by high performance liquid chromatography and flumetric detection. A homocysteine level above 15 mmol L(-1) was considered high. The mean fasting and afterload homocysteine were 15.28 and 31.29 micromol L(-1), respectively. Fasting hyperhomocysteinemia (>15 micromol L(-1)) was detected in 12% of male and 8% in female which significantly higher in men than women (p < 0.0001). Afterload methionine load homocysteine levels (> 31 micromol L(-1)) was detected in 16% of male and 14%in female which higher in men than women. Notably 80% of participants had normal total homocystein concentration (< or = 15 micromol L(-1)), but mild and moderate hyperhomocysteinemia was detected in 24% (n = 12). In this study, we find the difference between fasting and methionine afterload mean homocystein levels (p = 0.000), in 8% of those normal homocystein level, methionine afterload homocystein levels became abnormal. In conclusion, based on results, we recommend the methionine afterload homocystein levels in high risk cases with normal fasting level in order to unmissed some cases with normal basal homocystein level.