Background: Biliary phosphatidylcholine (PtdC) concentration plays a role in the pathogenesis of bile duct diseases. In vivo phosphorus-31 magnetic resonance spectroscopy ( 31 P-MRS) at 7 T offers the possibility to assess this concentration noninvasively with high spectral resolution and signal intensity. Purpose: Comparison of PtdC levels of cholangiopathic patient groups to a control group using a measured T 1 relaxation time of PtdC in healthy subjects. Study Type: Case control. Subjects: Two patient groups with primary sclerosing cholangitis (PSC, 2f/3 m; age: 43 AE 7 years) and primary biliary cholangitis (PBC, 4f/2 m; age: 57 AE 6 years), and a healthy control group (CON, 2f/3 m; age: 38 AE 7 years). Ten healthy subjects for the assessment of the T 1 relaxation time of PtdC. Field Strength/Sequence: A 3D phase-encoded pulse-acquire 31 P-MRSI sequence for PtdC quantification and a 1D image-selected in vivo 31 P spectroscopy for T 1 estimation at 7 T, and a T2-weighted half-Fourier single-shot turbo spin echo MRI sequence for volumetry at 3 T. Assessment: Calculation of gallbladder volumes and PtdC concentration in groups using hepatic gamma-adenosine triphosphate signal as an internal reference and correction for insufficient relaxation of PtdC with a T 1 value assessed in healthy subjects. Statistical Tests: Group comparison of PtdC content and gallbladder volumes of the PSC/PBC and CON group using Student's t-tests with a significance level of 5%. Results: PtdC T 1 value of 357 AE 85 msec in the gallbladder. Significant lower PtdC content for the PSC group, and for the female subgroup of the PBC group compared to the CON group (PSC/CON: 5.74 AE 0.73 mM vs. 9.64 AE 0.97 mM, PBC(f)/ CON: 5.77 AE 1.44 mM vs. 9.64 AE 0.97 mM). Significant higher gallbladder volumes of the patient groups compared to the CON group (PSC/CON: 66.3 AE 15.8 mL vs. 20.9 AE 2.2 mL, PBC/CON: 49.8 AE 18.2 mL vs. 20.9 AE 2.2 mL).Data Conclusion: This study demonstrated the application of a 31 P-MRSI protocol for the quantification of PtdC in the human gallbladder at 7 T. Observed differences in PtdC concentration suggest that this metabolite could serve as a biomarker for specific hepatobiliary disorders. Level of Evidence: 2 Technical Efficacy Stage: 3