As receivers of information from the media, we are faced with the constant problem of determining what sources are and are not credible. Given that much of what we know of the world around us comes directly from the media (Lippman, 1922), as receivers of messages from the media we realise how important the credibility of a news source is. Many of the attitudes that we form about a wide range of issues in society are formed as a direct result of the coverage we receive through the media, although there are numerous other factors involved such as issue involvement, intensity and closure (e.g., Guttman, 1954). Traditionally a large number of studies have argued that a high credibility source is more effective in causing attitude change than a low credibility source (Hovland & Weiss, 1951; Kelman & Hovland, 1953; Bochner & Insko, 1966; McGuire, 1973), while other experimental research examining the interaction between source credibility and other variables have indicated that there are other factors which have an important mediating effect on the impact of source credibility. To further complicate the issue, researchers have argued that credibility is not a stable attribute that a person assigns consistently to a source. Instead, credibility is highly situational and is a changeable perception by a receiver (Berlo, Lemert, & Mertz, 1969; Smith, 1970; Hayes, 1971; Chaffe, 1982). Also, individual differences of receivers such as age, education, gender, and knowledge about the media and the topic could contribute to the evaluation of source credibility (Westley & Serverin, 1964; Lewis, 1981). In addition, the importance of the issue in the media, the controversiality of the issue, receiver bias, the receiver's involvement with the issue and so on have also been shown to have a relationship with the evaluation of source credibility (Stone & Bell, 1975; Robert & Leifer, 1975; Gunther & Lasorsa, 1986). This thesis thus explores the various complexities involved in the relationship between media credibility and attitude formation by examining the characteristics that play a role in making a news source credible to readers, and then considering those factors that affect attitude change in the receivers of a news message. To achieve this, university students in south-east Queensland were examined in order to investigate attitude change regarding the issue of South Korea as a result of coverage in sources they perceive to be of high and low credibility. The study consisted of three stages: a survey of the university students to determine which newspapers they find to be of high and low credibility, a content analysis of their high and low credibility sources for articles of positive, neutral and negative tone, and finally an experiment which measured subjects' attitude change through reading articles of different tones in high and low credibility sources.