QUOTE(caeli @ Mar 3 2008, 08:12 AM)

I too am filing in London and it was made clear to me that the medical must be done prior to the interview because they must have the results at the interview and it takes several days for the various labs etc. to be ready, even based on the use of an express courier service (which you will have to pay for by the way).
The US Embassy in London Website has some really helpful information on all of this. It has been my primary resource as it gives information specific to filing with them. You will want to try to schedule the medical ASAP because there are only 2 clinics in London providing the service and they are almost always booked up for some time.
Sorry I think you will have to make two trips.
Regards,
Ang
Technically, this is not true. Quite a few VJers going through London have done the medical the day before the interview and the results are not yet at the Embassy -- as you say, it does take several days to get the results to the Embassy. However, on the day of the interview you will be told if you have been granted the visa subject to a satisfactory medical.
It isn't really impossible to do these back-to-back time-wise -- although the clinic is busy, it is always worth a punt asking for a specific date that suits you. Also, just to clarify, there is only
one outfit that provides the medicals -- Knightsbridge Doctors. They have two locations, but only one (Bentinck Mansions) provides medicals for US visas. The express courier service you pay extra for isn't for the medical, but for delivery of the visa, and even that doesn't get it faster to you -- you can just choose to have your visa delivered before a certain time.
Sorry to nit pick here! And I would agree that the Embassy website is a good source of info with one caveat: in some areas it is hopelessly out of date. (If it says the medicals are provided at two venues, that's one incidence!) The folks here on VJ who have recently gone through London do an excellent job at filling in the gaps.