The consistent reports on gender inequity in science achievement have led to a search for more effective strategies for correcting the imbalance. This study is part of a search which sought to investigate whether or not the cooperative-concept mapping technique improves the science achievement of girls. A non-equivalent control group quasi-experimental design involving three intact groups was adopted. Three schools and 362 Junior Secondary School (JSS) II (equivalent to 8th grade) students in Nnewi Urban, Anambra State of Nigeria constituted the sample. The subjects in each of the three groups were tested before and after treatment which spanned 8 weeks. The Test of Integrated Science Achievement (TISA) was used for data collection. Results showed that the cooperative-concept mapping strategy significantly improved the achievement of girls in the selected integrated science concepts. Contains 33 references. (Author/JRH)