1. Liposomes containing 111In-labelled bleomycin were injected intravenously into two patients. One patient had a hepatoma and the other had secondary adenocarcinomatous deposits in the liver.
2. The tissue distribution of 111In was determined by whole-body scanning and by measurement of the radioactivity in organs at autopsy.
3. Scans in vivo and post-mortem measurement of radioactivity indicated that liposomes accumulate predominantly in the liver, but that there is no selective uptake of liposomes by the malignant tissue.
4. The subcellular distribution of radioactivity in the liver was measured 90 min after injection by fractionation of percutaneous liver biopsies on sucrose density gradients.
5. Radioactivity within the liver was concentrated in lysosomes.
6. Electron microscopy of tissue obtained before the administration of liposomes revealed particles morphologically indistinguishable from liposomes in hepatoma cells and hepatocytes.