The paper sets out the known history as far as the Author's Company is concerned on operations involving the transfer of oil on the high seas. It then deals with the large scale lightening operations being undertaken by Shell in North West Europe and reaches the conclusion that these operations demonstrate that, given suitable shelter, lightening as a regular operation can be a perfectly satisfactory way of reducing the draft of incoming large tankers to enable them to enter restricted ports. Mention is made of the value of specialised lightening ships when mounting salvage operations for stranded tankers.