Purpose: High frequencies of GERD (58%) and MHDs (42%) were observed among exposed workers shortly after 9/11/01. We examined GERD and MHDs at two visits, 24.8±5.6 months apart, to see if their comorbidity persisted or changed. We also looked at the role of BMI, smoking, physical and psychological exposure. Methods: We studied the 697 Long Island patients in the WTCMMTP seen between 10/05-9/06 (V1) by a physician and completed questionnaires on medical history, psychometric measures, and exposure assessment. 413 (59%) patients came for a 2nd visit (V2). Diagnoses were based on: GERDclinical diagnosis; PTSD-Patient Check List; anxiety disorder- Patient Health Questionnaire (PHQ) and General Health Questionnaire (GHQ); depression-PHQ (at V1) or Center for Epidemiological Studies Depression Scale (at V2). At V2, PHQ and GHQ were not administered. Data was analyzed with SPSS 9. Results: Of the 697 patients, 92% were male and 71% were ages 34-50; mean BMI was 30. At V1, 41% (286) had GERD, more than the 20% found in the general population. Patients with GERD had a higher prevalence of each of the MHDs, at V1 and V2 (Table 1). At V1, patients with >1 MHD had progressively higher rates of GERD: No MHD 36.9%, 1 MHD 47.27%, 2 MHDs 64.4%, 3 MHDs 69.7% and 4 MHDs 72.2% (F=51.705, p<.000). 413 patients (59%) returned for V2: 55% had GERD. Smoking status did not affect the prevalence of GERD, at V1 or V2. Mean hours worked during September 2001 (mean 101, range 0-444) correlated with diagnosis of PTSD (r=.117; p<0.01) and GERD at V1 (r= .099; p<0.05). Among 33 workers with loss of a family member, 24% had PTSD, compared to 12% of the workers who had no such loss.Table: Effect of GERD on the prevalence of MHDsConclusion: The high frequencies of GERD and MHDs, seen in WTC workers just after 9/11, persist 4 and 6 yrs later. GERD patients are 2.13 and 2.65 times more likely to have PTSD and depression, respectively. GERD increases progressively among patients with ≥2 MHDs. Smoking and obesity were not associated with an increased frequency of GERD. Exposure hours were correlated with higher frequencies of GERD and PTSD. Thus, shortly after a highly stressful and toxic exposure, the appearance of GERD in a form characterized by high comorbidity with MHDs and no relation to smoking or obesity, suggests an important role for MHDs in its genesis and persistence. Treatment of the MHDs may be necessary for resolution of GERD symptoms.