This study investigated the effect of Systematic Desensitisation (SD) therapy on the reduction of test anxiety on some identified test anxious students. In addition, three secondary independent variables were studied along. These were entry test anxiety level, sex, and locus of control. A 2 x 2 x 2 way factorial design was employed. SD was found effective in the reduction of test anxiety of the students who were test anxious F-ratio= 9.261 with df (1,74). Entry test anxiety level of subjects was found to be significant on the level of reduction of test anxiety students F= 27.458 with df (1,74). Sex had no significant effect on the reduction of test anxiety of students F = 0.079 with df of (1,74) and p greater than 0.05. There was no significant interaction effect of therapy and secondary independent variables. However, there was a significant interaction effect of entry test anxiety level and therapy at the end of treatment. Since SD has been found to be effective in the reduction of test anxiety among adolescents in Nigerian schools; it is recommended that this therapy be used in the treatment of test anxiety. It should be noted that before the treatment of test anxiety, the entry test anxiety level of subjects must be considered so as to set a baseline for the therapy. (Contains 3 tables.)