The Southern District Health Board is apologising unreservedly for the loss of patient information in Dunedin.
It said a document was lost on Wednesday as a doctor was taking it between Pacific Radiology and Dunedin Hospital.
It said the paper, which has still not been found, carried the names and home towns of 26 patients, and some health information, but no specific addresses.
The board's chief executive, Chris Fleming, said it took patient privacy very seriously, and a full investigation will be done.
He said all the patients affected had been contacted, and will be given the results of the investigation.