The characteristics of the breeding water, interspecific association and seasonal abundance of 3 mosquito species within rice fields were examined in 6 districts. Larvae of Cx. antennatus were dominant (83.71% collected larvae), of An pharoensis were common (12.29%) and of Cx perexiguus were uncommon (4.0 = .0%). Breeding water has pH of 6-8, salinity of 0.05-0.35 gm Cl/L. and temperature of 21-29 degrees C. Although the relation of larval density (for each species) was positive with pH and negative with salinity and temperature however, no interaction (regression analysis) was existed among the variables (R = 0.26-0.40, P > 0.05). Significant and complete associations (CAB = 1.0, P < 0.01) were detected for Cx. antennatus with other species. During rice growing period (June to October), Cx perexiguus larvae were quite short lasting (June to August). Larval abundance varied monthly in relation to the plant growth stage. No larvae of any species were collected in short plant (< 20 cm, beginning of June) or in very long ones (130 cm in October). Higher numbers of larvae were often associated with the moderate plant growth (50-80 cm) with a peak in plants of 70 cm height in August (161.50 larvae/10 net dips for the 3 species). The highest larval density for Cx antennatus (132.50 larvae) and An pharoensis (22.25 larvae) were during August (70 cm plant) and for Cx. perexiguus (7.67 larvae) was in July (60 cm plant). So, rice fields are potential habitats for these disease vectors. The plant height and irrigation scheme are major factors affecting the abundance of these species.