Objective To provide scientific basis for quality control and clinical application via analysis and comparison of the contents and chemical components of the volatile oil in Mentha haplocalyx Briq,collected from Anhui,Hunan,Guangdong,Guangxi,and Jiangsu province. Methods The volatile oil was extracted by steam distillation. The chemical components of volatile oil were identified by GC-MS,and the relative contents of the components were calculated using peak area normalization method. Results The contents of...