Glaucoma patients are currently undergoing monitoring by community based optometrists as part of a randomised controlled trial of shared care. As part of this trial, the costs of monitoring these patients by community optometrists are being calculated. Data were obtained from eight practices for the 1993-1994 financial year. The average 'full' cost of a 40 min appointment was calculated as epsilon 31.56 pounds. The average number of unbooked appointments for the month of October 1994 was 16 per practice, which equated to 12, 40 min appointments. Once the number of unbooked appointments was surpassed for each practice, an average opportunity cost of epsilon 54.00 pounds was experienced per appointment. The participating optometrists were willing to accept a minimum fee of epsilon 26.03 pounds for a small number of patient assessments but this rose to epsilon 43.16 pounds for up to 100 glaucoma patients seen per annum.