RELMA Import error

Doing an import and receive this error message in a popup box…can someone assit with what this means and how to proceed? Thank you

Sorry but an error has occurred, do you wish to continue?

The changes you request to the table were not successful because they

would crreate duplicate values in the index, primary key, or relationship. Change

the data in the field or fields that contain duplicate data, remove the indes, or

redefine the index to permit duplicate entries and try again.