Phospholamban (PLB), an integral membrane protein of cardiac sarcoplasmic reticulum, was extracted from bovine cardiac muscle with an acidic chloroform/methanol mixture. A combination of gel permeation and ion-exchange chromatographies in organic solvents allowed the purification of PLB. The intensive use of organic solvents throughout the isolation yielded a highly purified and intact protein that can be phosphorylated by cAMP protein kinase. The ease of purification and the high yield obtained (2.5 mg/100 g of fresh tissue) show that organic solvents can be very useful in the extraction and purification of hydrophobic membrane proteins.