This is quasi experimental research that aims for knowing the effectiveness of Learning Cycle 3E model and conventional learning for increasing students mathematical conceptual understanding.  This research design is pre-test post-test control group design.  The research population is all students of 7^th grade class even semester of SMP Negeri 8 Bandar Lampung academic years 2012/2013 with homogenous student abilities. The research sample is 7^th A and 7^th D which  choosen randomly from seven classes.  Based on hypothesis analysis, it is found that students mathematical conceptual understanding average, and student from Learning Cycle 3E model is higher than conventional learning.  The conclusion is Learning Cycle 3E model is more effective than conventional learning for increasing students mathematical concept understanding.

Keywords: Effectiveness, Learning Cycle 3E, Mathematical Concept Understanding