Abstract: Milk is an important source of protein, fat, lactose, vitamins and minerals. The nutritional value of milk from various animals, such as the highly popular cow milk, contains many useful nutrients. However, milk consumption is restricted for some consumers because they are allergic to milk. Milk allergy can be found in children and adults alike. In children, allergy symptoms include diarrhea and vomiting while the symptoms in adults include flatulence, indigestion and stomach gas. These symptoms are a result of the body’s inability to digest lactose in milk due to the lack of necessary enzymes that can digest milk. A study discovered that East Asian and North American populations have the highest rate of lactose intolerance of 80-100%, followed by the Middle Eastern population at 80%. The United Kingdom population has the lowest rate of lactose intolerance at 5-15%. Lactose-free milk for adults is not yet commercially available in Thailand. Therefore, the researchers are interested in studying the level of knowledge on lactose-free products and factors influencing the intention to purchase lactose-free milk for the population of Bangkok. The researchers hope that these findings will be used to develop a guideline for suitable marketing strategies of lactose-free milk in Thailand. These findings can also provide basic information for the government sector to formulate appropriate public health plans for populations with lactose intolerance. This research used both quantitative and qualitative approaches. The scope of the research was limited to consumers over 18 years in Bangkok with total study samples of 500 subjects. The quantitative techniques used were Path Analysis and Partial Least Square (PLS-Graph program) while the qualitative technique used was in-depth interview with individuals in the related fields of nutrition and food and beverage marketing. There were a total of 10 interviewees who were physicians, nutritionists and marketing experts.The research found that the factors influencing the intention to purchase lactose-free milk include consumer characteristics (age and health conditions), knowledge of lactose-free milk (consumer knowledge, public relations and brand reputation) and milk consumption behavior (milk quality and price acceptation).