Mathematics teachers need to be knowledgeable in mathematics before they can help students to learn mathematics meaningfully. In particular, the subject matter knowledge (SMK) of mathematics is essential in planning of classroom instructions. Studies on SMK had gained the attention in mathematics education community. Nevertheless, it is noted that most of the past studies about teachers' SMK has been general in nature and not topic specific (Even, 1990). This paper attempts to examine a pre-service secondary school mathematics teachers' SMK of a specific mathematical topic, namely perimeter and area. Clinical interview technique was employed to collect the data. This paper presents the analysis of the responses of a case study, named Chan, related to a particular task. The results showed that Chan has procedural knowledge and limited substantive knowledge of perimeter and area. He was not able to explain the concepts underlying the area formulas. Chan's knowledge about the nature and discourse of perimeter and area was also limited. He was concerned with 'getting an answer' without checking the reasonableness of his answers. His notion of 'doing' area measurement was highly formula bounded.