A simulation model of double-16 and double-20 herringbone and parallel milking parlors and double-32 and double-40 parallel milking parlors was used to examine the effects of size, design, operating characteristics of the milking system, management strategies, and milk yield on parlor performance. Analysis of factorial experiments indicated that smaller parlors were more efficient. Turns per hour and milk per stall per hour for double-16, -20, -32, and -40 parallel parlors were 5.87, 5.91, 5.21, and 5.00 turns/h and 56.19, 56.46, 49.66, and 47.94 kg/h, respectively. A wider pulsation ratio (60:40 to 70:30) increased performance measures about 4%, and increased vacuum pressure (46.6 to 50.8 kPa) increased performance measures > 6%. Parallel parlors outperformed herring-bones by nearly 8%. Abbreviated milking procedures resulted in a > 6% increase in performance measures over standard milking procedures. Performance response was significantly diminished when the amount of milking labor exceeded deficit amounts (20 to 32 units per milker) for abbreviated milking procedures or standard amounts (13.3 to 16 units per milker) for standard milking procedures. When milk yield increased, turns per hour decreased, but milk per stall per hour increased.