To know what is going on in physicians' surgery hours, assessment of practice performance is important with regard to quality assessment activities. The incognito standardized patient (SP) method is a powerful method to assess this. However, until now no reports have been published about specialists' performance using this method. In this study, 27 rheumatologists in 16 hospitals were each visited by eight incognito SPs to study the feasibility of sending incognito SPs to specialists working in different hospitals, of follow-up consultations and of simulating additional investigations. SPs recorded performance on case-specific checklists. The different steps needed for these visits are described in detail. A total of 136 first and 32 follow-up visits took place. SPs remained undetected in 98% of the visits. It is concluded that this SP method is a feasible one, however, only to be used for very specific purposes. Use of incognito SPs for larger scale projects is not recommended.