Abstract: A multi-lobe gradient cam for a high performance liquid chromatography pump for controlling proportions of HPLC solvents on the low pressure side of the pump. The gradient cam is non-concentric, and has an upward or draw gradient ridge over a majority of its circumference and a downward or thrust gradient over a minority of its circumference. In operation, the cam is designed to be used with two followers, located 180.degree. apart, which follow along the cam's gradient. The unique cut of the multi-lobe cam insures a constant suction on the inlet or suction side of the cam during the entire pump cycle.