When you buy 10 tickets at once; note that ticket sellers often can't change large bills. You insert the ticket into the turnstile at the platform entrance, and it's returned to you only if there's unused fare on it. Transfers within the metro system are free, as are bus-to-metro (or vice-versa) transfers. You can buy a bilhete integração (integration ticket) on buses or at metro stations for R$3.60. You can print maps from the English-language Web site of the Metrô, where you can also find ticket prices and schedules.
Metrô (011/3286-0111. www.metro.sp.gov.br).
