Anti‐hormone‐sensitive lipase (HSL) immunoglobulin selectively immunoprecipitates a single 84 kDa ³²P‐phosphoprotein from macrophage homogenates previously phosphorylated by cyclic AMP‐dependent protein kinase in the presence of [γ‐³²P]ATP‐Mg. This immunoglobulin also completely removes the neutral cholesterol ester hydrolase activity from macrophage homogenates. These data demonstrate that HSL is responsible for the neutral cholesterol ester hydrolase activity in macrophages and hence plays a key role in cholesterol metabolism in these cells.