One major policy of the Tourism Authority of Thailand is to promote domestic tourism. In Thailand, the family is considered to be the main social group, and as such is the main target for domestic tourism marketers. However, relatively little is known about family decision making, especially in Thailand. This thesis addresses this gap in knowledge by employing a two-staged conjoint study to examine the preferences and the influence of family members in a destination choice decision. At the first stage (an in-home interview), family members were asked to provide their holiday destination preferences and their estimation of the other family members' preferences. At the second stage (an in-home interview two weeks later), they are asked to provide their estimation of the joint family preferences, after being provided with a table listing the individual family members' preferences. Finally, they were asked to make the holiday destination decision as a family. This design allowed three thesis aims to be addressed: 1) to examine individual family members and the family group preferences; 2) to examine the ability of family members to predict other family members' preferences and their influence on the family decision; and 3) to examine family members actual influence of family members on the family decision. The findings revealed considerable similarities in the importance of attributes, with price and destination being more important, as well as the levels, with the majority preferring a lower rather than higher price and a beach rather than mountain destination. Further, there was reasonable accuracy in the prediction of each others' preferences, although parents were more accurate than children. However, there was a considerable amount of inaccuracy in the prediction of each others' influence. Family members systematically overestimated their own influence, and underestimated the influence of other family members.