Recently, one of our customers compared our lentiviral packaging mix with packaging mixes from two competitors. The same lentiviral vector that expresses firefly luciferase was used in all three packaging protocols. Each lentivector was packaged according to the manufacturer’s instructions in 293T cells. Collected virus was used fresh to transduce 293T cells for 48 hr. Firefly luciferase activity was assayed using a standard protocol and compared to untransduced cells.