A study of the quality of 637 referral letters from general practitioners (GPs) and corresponding reply letters from medical specialists showed that both types of letters can be improved, and that specific requests by GPs were addressed explicitly by the specialists in only a limited number of cases. Better referral letters resulted only partly in better reply letters. A letter is considered to be of higher quality when a specialist commences a letter with a reference to the specific request by the GP. In conclusion, opportunities for optimal communication should be better used.