This study aims to research on the validity and reliability of concept maps and structured communication grids used to assess students' achievement regarding the unit called "Newton's Laws of Motion". The sampling consisted of 102 students studying in their Year One at Science Teaching and Physics teaching departments during 2009 - 2010 academic year. The responses to the short-answer test consisted of the main measure in checking the validity of the concept map and the structured communication grid. The Pearson Correlation Coefficient between the scores of the short-answer test and the concept map was calculated to be 0.57. In order to find the reliability state of the concept map, the calculation concluded as 0.69. The degree of the relationship between structured communication grid and short answer test scores was calculated (0.69; p<0.05). For the reliability of the structured communication grid, Cronbach Alpha was calculated 0.77. A positive, medium level and significant relationship was observed between the structured communication grid and the concept map (0.51; p<0.05).