['To evaluate the association between gamma-glutamyl transferase (GGT) and homocysteine in plasma.', 'Combined results of GGT, total homocysteine, vitamin B12, folate and creatinine levels were analyzed in outpatients referred for laboratory testing over the past 5 years.', 'Cumulative results for homocysteine, GGT, B12, creatinine, folate could be retrieved for 449 outpatients > 35 years old over the study period. The concentration of homocysteine significantly increased among tertiles of GGT activity. In multivariable linear regression analysis, GGT activity was independently associated with homocysteine concentration, independent of age, gender, folate, vitamin B12 and serum creatinine levels.'] Does plasma gamma-glutamyl transferase activity predict homocysteine concentration in a large cohort of unselected outpatients?