This paper explores whether service reliability determines transit patronage. Using a unique historical archive of service supply, performance, and patronage data from the Los Angeles Metro bus and rail system, we analyze whether service reliability explains in part the variation in patronage across transit lines during weekday peak and off-peak periods. By estimating a simple single-stage model of transit line patronage, and a simultaneous equations model to address the recognized endogeneity between transit service supply and consumption, we provide conclusive evidence that service reliability is indeed a significant determinant of peak-period patronage. This means that, all else equal, more reliable transit lines can attract more patrons across their service corridors as they are chosen over alternate lines and competing modes. Our paper presents first empirical evidence on the demand for transit service reliability. Results suggest that transit agencies can expect some system-wide patronage gains from reliability improvements. From a policy perspective, reliability investments may be cost-effective means for increasing productivity of transit lines and systems.