Declining response rates and rising levels of non-coverage associated with the growing penetration of mobile phones pose challenges to conventional telephone surveys based on fixed line RDD. These problems have been recognised for some years in the United States, where an AAPOR commissioned task force produced national reports in 2008 and 2010 highlighting the issues that arise when mobile phones are incorporated into telephone surveys. Surveying mobile phone users introduces new complexities in coverage and sampling, nonresponse, measurement, weighting, legal and ethical issues and cost that survey researchers must address. In Australia in January 2010 approximately 86% of households had landlines while approximately 14% of mobile phone users did not have a landline connection; moreover the proportion of “mobile phone only” households continues to grow. Despite this there has been very little Australian research about how to incorporate mobile phones into telephone surveys and about the consequences of excluding mobile phone users. This paper reports on one of the first dual-frame surveys conducted in Australia, a national omnibus survey undertaken by The Social Research Centre in December 2011. Through a comparison of the fixed line and mobile phone samples, the paper illustrates some of the consequences of failing to include mobile phone users in telephone surveys, and examines and evaluates some of the different approaches to combining results from these samples in dual-frame designs.