The purposes of this research were to study the relationship between social support, selected factors and anxiety in pregnant women and to compare the levels of anxiety and social support at different stages of pregnancy. The rescarech sample were 210 pregnant women who attended ante-natal clinic at Chulalongkorn Hospital. Thirty-five of them were in the first trimester 70 and 105 were in the second and third trimester respectively. Data were collected using interview and questionnaire. The results revealed as follows: 1. The levels of anxiety of pregnant women in the first, second and third trimester were not statistically different. 2. The pregnant women in the first, second and third trimester received different social support as well as emotional and material support from husband at .01 level of significant. 3. The pregnant women in the first, second and third trimester received social support from husband more than receiving from others at .01 level of significant. 4. The levels of anxiety in pregnant women were negatively correlated to social support as well as emotional, information and material support from husband at .01 level of significant. The negative correlation was also found between emotional and material support from others and the pregnant women anxiety at .01 level of significant. 5. In the first trimester, the pregnant women levels of anxiety was negatively correlated with social support. However, it was found no statistical significant. 6. In the second trimester, the pregnant women levels of anxiety were found negatively correlated to emotional support from husband and to material support from others at .05 and .01 levels respectively. 7. In the third trimester, the pregnant women levels of anxiety were found negatively correlated to social support, emotional, information and material support from husband at .05 level of significant. It was also found negative correlation between social support and emotional and material support from others at .01 level of signifiant. 8. Factors that could predict the differences of the pregnat women levels of anxiety were emotional support from husband and material support from others. When stages of pregnancy were determined it was found that: There was not any factor that could predict the levels of anxiety of pregnant women in the first trimester. Age and family types could predict the levels of anxiety of pregnant women in the second trimester. Emotional support from husband and material support from others could predict the levels of anxiety of pregnant women in the third trimester.