The need of diagnostic testing arises in the subject mathematics specifically at the time when a particular student exhibits some of the other signs and symptoms of his failure or difficulties with regard to the learning of the subject mathematics. Why is one subjected to repeated failure in the subject mathematics? Why is he feeling difficulty in learning a particular concept or skill in one or the other branches and topics of mathematics? Why is he not attending the classes in the subject mathematics? Why does he create fuss or problems in the mathematics class? Why does he hate the teacher of mathematics and his subject? The list may be quite exhaustive with regard to such day to day or occasional problems faced by a teacher of mathematics with his one or more students. It can be easily concluded from the above discussion that diagnostic testing and: remedial teaching are inter-related and complementary to each other. However, the diagnosis not followed by the remedial treatment is useless. Similarly, a remedial task not based on the diagnosis of the nature and extent of the weaknesses may prove not only the wastage of the resources but can also prove dangerous to the well being of the affected persons. It is, therefore, essential that diagnostic testing in mathematics should necessarily be followed by the suitable remedial teaching.