This descriptive – correlational method of research ascertained the teachers’ and students’ mastery of the competencies for Science and Technology II in secondary public schools in San Joaquin, Iloilo. Conducted in March 2010, this study utilized a Questionnaire-Checklist and Mastery Test in Science and Technology II for data gathering. The statistical tools used were t-test, Pearson’s r, standard deviations, means, rank, and frequency. Alpha level was set at 0.05. The study revealed that the mastery level of teachers when grouped as a whole was well-mastered. The students’ mastery level of the competencies for Science and Technology II when taken as a whole group was Nearly Mastered. There was no significant difference in the teachers’ mastery level of the competencies for Science and Technology II when they were grouped according to degree program. Likewise, they were not significantly different in terms of mastery level of the competencies when they were classified as to length of teaching experience. However, a significant difference was noted when teacher respondents were grouped according to number of teaching preparations. Teachers’ mastery of the competencies in Science and Technology II varied significantly when they were categorized as to number of teaching preparations. Moreover, significant positive relationships were found between the teachers’ and students’ mastery level of the competencies for Science and Technology II. The competencies for Science and Technology II mastered by both teachers and students were: (1) Explain the different life processes; (2) Identify the unifying ideas in biology; (3) Name the special tools used in research and technology; (4) Describe the cell cycle; (5) Identify the parts and functions of the microscope; (6) Recognize the necessity of an organized system for proper growth, development and survival of plants, animals, and human organisms; (7) Explain osmosis as a type of diffusion; (8) Solve monohybrid crosses given the phenotypes and genotypes of parents; (9) Identify the traits that follow Mendelian patterns of heredity; (10) Differentiate mitosis from meiosis. In terms of the problems encountered by biology teachers when using the Philippine Secondary School Learning Competencies (PSSLC’s) for Science and Technology II, the top ten significant problems were: (1) the need of the existence of a functional biology laboratory; (2) the ample supply of chemical reagents and laboratory equipment for a biology class; (3) the ease in acquisition of commercially available laboratory equipment; (4) the availability of basic laboratory apparatus for a biology laboratory course; (5) sufficient instructional materials in the school’s instructional center; (6) full support from the local school board for professional upgrading of teachers; (7) the access to and availability of books, activity guides and supplementary reading materials; (8) acceptable class size of 30 – 40 students in a biology laboratory/lecture room; (9) the provision for a well lighted and well ventilated science classroom, planning and (10) planning and implementing satisfactorily routine activities in handling science materials, equipment and supplies.