This study examine of retention capacities of students taught with prior knowledge of electrical installation and maintenance works instructional objectives in technical colleges. Two research questions and two hypotheses guided the study. The design of the study was pre-test, post-test, non-equivalent control group quasi experimental study. The study was carried out in Enugu State in the present South East Zone of Nigeria. The population for the study was 1,115 year two Electrical Installation and Maintenance works students in the 19 technical colleges in the State. One technical college which offers Electrical Installation and Maintenance works was randomly chosen from the six educational zones in the State for the study. The total number of students in their intact classes who offered Electrical Installation and Maintenance works in these colleges was 326. This formed the sample for the study. 249 (79.4%) of the students were male and 77 (23.6%) were females. The instrument used for data collection was the Electrical Installation and Maintenance Achievement Test (EIMWAT). This had three versions Pre-test, Post-test and Retention tests which were the same except for the swapping of all the options for each answer for the 30 questions used for the study. The instrument was subjected to both face and content validation and item analysis. The reliability of the instrument was established Using Kuder Richardson (K-K) 20, the internal consistency was found to be 0.78 using Pearson r, the test retest stability measure was found to be 0.96. Pre-EIMWAT was administered by the beginning of the five weeks treatment period. Post EIMWAT was administered at the end of the five weeks treatment period. After two weeks of administration of Post –EIMWAT, the retention test were administered. Scores from Pre-EIMWAT, Post-EIMWAT and retention tests were analyzed using means, standard deviation and Analysis of Covariance (ANCOVA). Some of the major findings from the analysis were: (1)there is a significant difference in the mean retention scores of technical college students taught electrical installation and maintenance works with prior knowledge of instructional objectives and those taught the same topic without prior knowledge of the instructional objectives, and (2) prior knowledge of instructional objectives before instruction can effectively close the retention gaps between male and female students in Electrical Installation and Maintenance works and most probably other technical and vocational subjects. The study recommended that (i) Both Federal and State Ministries of Education should study the analysis of this study with a view of establishing pilot schools to authenticate the findings of this study. This, in turn is expected to result in the generalization of this innovative approach in Nigerian schools and (2) Professional bodies in vocational subjects should organize seminars and workshops on how teachers should educate both genders collectively without any bias in technical subjects in colleges