Key Informant interviews with staff at social hygiene clinics also revealed the difficulties of keeping track of workers' attendance at the clinics. If-but only if-a sex worker has a yellow registration card, the clinic can check if she comes back. She may also miss 1 month and return the next. Several factors account for this irregular use. First, not all managers cooperate because they are concerned about their business. Moreover, workers may not know about, or forget, their appointments. Or they may choose to see other doctors, especially if their managers arrange appointments for them.