A great number of misconceptions in diverse subject areas as well as across age levels have been documented and described. Photosynthesis is one of the more intensively studied areas in biology. The purpose of this research was to carefully select and define misconceptions about photosynthesis needing remedial efforts. To achieve this, a specially designed paper-and-pencil test was administered to 285 students in grades 11 and 12 who had previously completed a study of photosynthesis just prior to the test. Analyzed in this paper were the results of the limiting factor activities, and items which tested the concept of the relationship between photosynthesis and respiration. It was found that even though these students were familiar with the concept of limiting factors, they had trouble applying it in everyday life; the students' understanding of the latter concept was as a gas exchange rather than as a biochemical process. Recommendations for the production of remedial materials are provided. A list of 21 references is included. (CW)