This study was aimed at finding out if the level of performance of selected Jamaican Grade 12 students on an achievement test on the concept of genetics was satisfactory; if there were statistically significant differences in their performance on the concept linked to their gender, self-esteem, cognitive abilities in biology, school-type and socioeconomic background (SEB); and if there were significant correlations among the five variables and the students' performance. The sample (n = 357, 102 males and 255 females) was chosen from two all-boys' schools, four all-girls' schools, and 13 mixed schools in rural and urban Jamaica. The results indicated that the students' level of performance (mean = 22.81 or 45.62%) was unsatisfactory; there were statistically significant differences in the students' performance on the genetics test based on their self-esteem, cognitive abilities in biology and school-type in favour of students with a high self-esteem, high cognitive abilities, and students in the coeducational schools respectively; there was a positive, statistically significant but weak relationship between the students' (a) self-esteem, (b) cognitive abilities, and (c) school type and their performance on the genetics test. (Contains 5 tables.)