Background: Hyperemesis gravidarum is a high disorder characterized by ongoing severe nausea and vomiting affects 0.3–3% of women during pregnancy. Hyperemesis gravidarum badly affected the general health condition of pregnant women. Aim of study: Was to assess knowledge and practices of pregnant women regarding hyperemesis gravidarum. Study design: A descriptive study was utilized to conduct this study. Setting: This study was conducted at Obstetrics and Gynecological inpatient departmentand outpatient clinicat Benha University hospital. Sample: A purposive sample was used 50 pregnant women suffer from hyperemesis gravidaurm were admitted to the previous setting for eight months. Tools of data collection: Data were collected by using one tool: A structured-interviewing questionnaire sheet which consisted of three parts, part I: Socio-demographic data, part II: Knowledge assessment sheet and part III: Maternal health practices questionnaire. Results: There was less than two-thirds of the studied women had poor knowledge regarding hyperemesis gravidarum; while less than one-third of them had good knowledge. Regarding to healthy practices of mothers, less than three-quarters of mothers had unsatisfactory healthy practices and less than one-third of them had satisfactory healthy practices regarding hyperemesis gravidaurm. Conclusion: There was a highly positive statistical correlation between total knowledge and total practices regarding hyperemesis gravidaurm. Recommendations: Designing, implementing and distributing guidelines for hyperemesis gravidarum through antenatal clinic during initial visit of the pregnant women.