This article provides an empirical test of the theory that individuals gath
er political knowledge by inferential reasoning- constructing political "re
ality" from the messages to which they are exposed by making inferences abo
ut what they do not know based on extrapolations from what they see or hear
. This "filling-in" may often result in misinformation:, or the belief in i
ncorrect information (as distinguished from a simple lack of information, o
r ignorance). Widespread misinformation among the electorate changes our co
nception of democracy as a "marketplace of ideas," and may have much more s
erious consequences than does a broad Lack of information or sophistication
on the part of the electorate. Data from a 1997 random-digit-dial survey o
f 810 adults residing in San Diego was used to test the hypothesis that lis
tening to political talk radio leads to higher levels of both information (
regarding non-ideologically charged facts) and misinformation (regarding id
eologically charged facts). Analysis revealed that active listening (not on
ly listening but also calling and/or taking action because of talk radio) c
orresponded to higher levels of information, regardless of the ideological
nature of the talk radio programs to which the listeners were exposed. Howe
ver, greater frequency of exposure to conservative talk radio independently
corresponded to greater misinformation, while greater exposure to moderate
programming was associated with being less misinformed, controlling for pa
rtisanship, ideology, and a number of other predictors.