BACKGROUND AND AIM: The use of glyphosate-based herbicides has increased significantly over the past 25 years. Globally, they are now the most widely used pesticides. Few studies have documented human rates of glyphosate exposure nor potential linkages with liver disease. We present findings of 2 studies conducted by the UC San Diego Herbicide Awareness and Research Project. METHODS: Study 1: Among 100 randomly selected participants of the UC San Diego longitudinal Rancho Bernardo Study we measured urinary glyphosate concentrations at 5 time points between 1993 and 2016. Study 2: Glyphosate excretion was examined in the context of incidence of non-alcoholic liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) among 100 patients from the UC San Diego NAFLD Research Center. For each study, urine samples were analyzed using high-performance liquid chromatography coupled with mass spectrometry. Limits of detection (LOD) for glyphosate were 0.03 μg/L; assays were linear up to 50 μg/L. Analyses were normalized to each sample’s specific gravity, thereby accounting for dilution or concentration effects due to variability in water intake and age-related or other differences in renal function. RESULTS:Study 1: Mean glyphosate exposure increased 1000% over the period. From 1993-1996 to 2014-2016, mean sample values increased from 0.024 μg/L to 0.314 μg/L (p0.001) and mean rates of exposure increased from 0.120 to 0.700 (p0.001), respectively. Study 2: Glyphosate excretion was significantly elevated in patients with NASH as compared with patients without NASH (p=0.01) and in patients with more severe liver fibrosis (p=0.01). CONCLUSIONS:Glyphosate exposure has increased significantly since GM crops were first introduced into the US food supply in the early 1990s. Consistent with over 8 animal feeding studies, in humans, chronic exposure to glyphosate may be associated with incidence of fatty liver disease, an epidemic in the US. KEYWORDS: pesticides, other (liver disease)