This study tries to identify the effect of assessment for learning on a group of Sudanese pre-medical students' performance in English for Specific Purposes (ESP). The study also attempts to identify students' perception and attitudes towards this type of assessment. The sample of the study is composed of 53 subjects from the Pre-medical students at Khartoum University in Sudan. These students are placed into two groups; an experimental and a control group. The experimental group students are taught their ESP material in accordance with assessment for learning principles and techniques, the control group; however, is taught the same material using the traditional summative assessment procedures. The experiment lasts for one term, i.e., 16 weeks. The experimental group instructor is subjected to an intensive training course on how to implement assessment for learning strategies in classroom setting. At the end of the term, the two groups sit for a final exam which is intended for all Pre-medical students. Comparison of the scores of the students reveals a significant difference between the two groups in favor of the experimental group. Students' attitudes towards assessment for learning are checked through a questionnaire and interviews. Qualitative and quantitative analysis of the students' responses show their positive attitudes towards this type of assessment. The study ends up with a set of recommendations and suggestions to improve assessment for learning practice and to make it more effective in a Sudanese setting.