Objective To evaluate the influence of single HD on c-type natriuretic peptide(CNP) and cardiodilatin(CDN). Methods Eighteen maintenance hemodialysis patients were studied. Blood samples were collected and blood pressure were measuredbefore hemodialysis, 1, 2, 3, 4 hours duning hemodialysis and post hemodialysis. CNP and CDN were measured with radioimmunoassay(RIA). Results The value of CNP before HD is significantly lower than all the others; There was no significant difference between the other 5 groups. the means of all the 6 groups were higher than the normal referenle ralue (NRV). 2, The NRV of CDN is from 210 to 260ng/L. The means of the before and after HD group were higher than the other 4groups during HD and NRV. The means of the 4 groups during HD were within the NRV. There was no significant difference between all the 6 groups. 3, There were positive correlations befween CNP and systolic pressure and CNP and diastotic pressure. Conclusion Many angio-bioactive peptide are influenced by chronic renal failure and HD. The CNP value in maintenance hemodialysis patients are higher than NRV and increase gradually during hemodialysis. The CDN value before and after hemodialysis are highention NRV while decreases and are with in NRV during HD. There are positive correlation between CNP and systolic pressure and CNP and diastolic pressure.