Malaysia is in the process of changing the medium of instruction for mathematics and science from Malay to English since 2003. To ensure the success of this transition, teachers have to be professional prepared to teach in English. This research aimed to survey the Malaysian science/ mathematics teachers' perception towards this professional preparation effort. The findings showed that although the teachers perceived they are professionally prepared to teach mathematics/science in English, they still need more preparation in overcoming students' difficulties in learning the subjects in English especially for students who are weak in English or mathematics/science or both.