The quality of referral letters to the gynaecologist compared with the standard of the Dutch Association of General Practitioners. OBJECTIVE. To assess the quality of referral letters of general practitioners (GP) used to refer new patients to a gynaecologic outpatient clinic. DESIGN. Prospective study. SETTING. Gynaecologic outpatients' clinic, Medical Centre Alkmaar, the Netherlands. METHOD. The actual quality of referral letters was compared with ideal quality, as defined by the Dutch Association of General Practitioners (NHG) in 1989. RESULTS. Fifty-three (14%) of the 373 new patients did not have a referral letter: 23 women (6%) consulted the gynaecologist without having consulted their GP first. Of the 320 referral letters 63% conformed to the NHG criteria and 27% contained a specific question to the specialist. One hundred and fifty-two letters (47%) were handwritten, of which 32 (10% of the total) were hardly legible. A good to excellent letter had a length of slightly more than 6 to 8 lines (A4 size). CONCLUSION. Of all 320 letters analysed 15% was qualified as 'excellent', 48% as 'reasonable/good', 25% as 'brief/just adequate' and 12% as 'inadequate/insufficient'.