This descriptive study identified and assessed the competencies of grade four science teachers as perceived by the administrators and the teachers themselves. It also ascertained the determinants of science competencies and the relationship of teachers' competencies to pupil achievement. Cluster sampling was used involving grade four science teachers and their pupils as well as administrators in the Division of Iloilo. The statistical tools were: the arithmetic mean, rank order, weighted mean, t-test for independent samples, stepwise multiple regression analysis, Pearson Product-moment coefficient of correlation, and analysis of variance. The results showed that the most important teaching skill perceived by administrators and teachers was "choosing science lessons suited to pupils" needs, interest and abilities" and the least important was "providing challenging activities for gifted pupils and remedial measures for slow learners." For classroom management skills, the most important was"providing a permissive and stimulating atmosphere that encourages pupils to raise questions and suggest alternative solution to problems". Storing science books, materials, equipment, facilities, etc. as mostly and efficiently as possible" came out as least important. For evaluation skills, "setting up criteria for accurate evaluation of pupils' performance " was considered the most important and using informal evaluation procedures for collecting and interpreting data", the least important. Instructional skills, classroom management skills, and evaluation skills were found to be significantly interrelated. Teachers' competence and final grades in science were significantly related. Classroom ventilation and lighting, number of daily preparations and frequency of science seminars attended were the determinants of science competencies. Teachers and administrators did not differ in their perceptions of teaching skills and classroom management skills necessary for a competent science teacher to possess, but their perceptions of the evaluation skills differed significantly. Instructional skills, classroom management skills and evaluation skills differed significantly due to the main effect and interaction effects of some personal and school factors.