As cell-based assays are used more commonly in robotic high-throughput compound screening, cells themselves have become critical reagents. Thus, it has become essential to produce cell reagents with high consistency and quality. We experimented with cells division-arrested with low-level mitomycin C treatment and demonstrate that they perform with better consistency than non-division-arrested counterparts in high-content screening imaging assays. We propose that for cell-based screening, it is possible to uncouple the cell production process from the screening process. Cells can be produced en masse, treated to become irreversibly division-arrested, and cryopreserved. These "ready-to-use" reagents can be thawed, plated, and used in screening with improved consistency and convenience.