In order to prevent farmers working in greenhouses from developing occupational low back pain, the relationship between working space and working posture was examined. Out of 61 greenhouses, the working space of 57 greenhouses was measured as a function of the height of the plant stems and the width of the pathways, The author demonstrated that the height of the stem was the best indicator of the working space. The results of a study of the relationship between working space and working posture showed that the narrower the working space is, the more frequently farmers worked in an unnatural posture. The prevalence of low back pain among 144 farmers working in eggplant greenhouses was examined. A negative correlation was observed between the prevalence of low back pain among the farmers and the width of their working spaces.