My old biology teacher once told me a story about a friend of his in order to help me remember just what the effectn of Antidiuretic hormone are. At the time, both were at university. His friend had drunk away most of his money, and so signed up for some experiments at the local medical school (This was London - there are several of the things about). In this instance, they were investigating the degree to which water retention was increased when ADH was administered in distinctly non-physiological concentrations.

So, they injected him with a large quantity of ADH and then gave him several litres of water to drink. After a few hours, he still hadn't urinated. Apparantly deeming the experiment a success, the researchers (probably a jumped-up bunch of medical students who enjoyed inflicting pain on others - it seems pretty standard practice (1)) gave him his money and kicked him out.

The scene now shifts to an Underground station. Those of you who have visited London will probably be aware that public toilets were not a priority when the Underground was built. It is approximately midnight. The ADH decides to take the opportunity to drop back within the realms of normal levels. Our hero was suddenly left with several litres of excess water in his bloodstream and kidneys that were working overtime to remove it. Faced with a five minute wait until the next train and having no chance of making it back above ground, he ran to the end of the platform and relieved himself at quite some length. By some miracle he managed to avoid being electrocuted, but as he gasped in relief, he was tapped on the shoulder by a member of the Transport Police and spent the night in a cell with a toilet in the corner.

And that's how I manage to remember that antidiuretic hormone causes increased water retention.

(1) Yes, I have been a medical student. Can't you tell?