A novel non-flow approach for high-speed optical assays of microliter sample volumes is described. The method is based on the passage of well-defined sample zones, emerging from a computerized pipette, through a radiation path. Sharp absorbance transient peaks accrue from the reproducible travel pattern of the intact samples. Measurements are performed within a modified sample compartment of a conventional spectrophotometer. Repetitive optical measurements at very high rates of 360–1800 samples per hour yield relative standard deviations of 0.3–0.7% with no observable carry over. Such performance characteristics, coupled with the simplicity and low cost, hold a great promise for routine automated assays.