Depending on when the collection agency obtained this information, yes it could be a violation of HIPAA.  You are absolutely correct that a third party collection agency who is seeking monies for medical services you have not paid for should not need nor have cause to have your medical details.  The only item that collection agency needs is the amount you owe and when it was incurred. You may wish to consult with an attorney who specializes in HIPAA because there may be federal and state statutory issues here that can help you recover certain costs possibly, even forgiveness of debt if you negotiate it properly. Every state has an option to make its laws stricter than the federal HIPAA legislation, so oftentimes it is not an issue of federal pre-emption as much as it is an issue of which law the court will indicate it will use.