Abstract Purpose Moderate-to-high correlations have been reported between the [¹¹C]PiB PET-derived relative tracer delivery rate R₁ and relative CBF as measured using [¹⁵O]H₂O PET, supporting its use as a proxy of relative CBF. As longitudinal PET studies become more common for measuring treatment efficacy or disease progression, it is important to know the intrinsic variability of R₁. The purpose of the present study was to determine this through a retrospective data analysis. Procedures Test-retest data belonging to twelve participants, who underwent two 90 min [¹¹C]PiB PET scans, were retrospectively included. The voxel-based implementation of the two-step simplified reference tissue model with cerebellar grey matter as reference tissue was used to compute R₁ images. Next, test-retest variability was calculated, and test and retest R₁ measures were compared using linear mixed effect models and a Bland-Altman analysis. Results Test-retest variability was low across regions (max. 5.8 %), and test and retest measures showed high, significant correlations (R²=0.92, slope=0.98) and a negligible bias (0.69±3.07 %). Conclusions In conclusion, the high precision of [¹¹C]PiB R₁ suggests suitable applicability for cross-sectional and longitudinal studies.