Methods and apparatus to collect audience information associated with a media presentation are described herein. In an example method includes counting a first number of individuals proximate to a media presentation device, counting a second number of signals received from one or more portable devices, each of which is associated with a respective one of one or more monitored individuals, comparing the first number of individuals to the second number of signals, and determining a third number of unidentified ones of the individuals proximate to the media presentation device based on the comparison of the first number of individuals to the second number of signals.