Data tapes containing the personal details of 34,000 Boots customers and employees have been stolen from a security courier.
The tapes were taken from the car of a subcontracted data security company in Bristol on 3 April. Boots declined to name the courier company.
The stolen data tapes included names, addresses and bank details of 27,000 dental plan customers, which is run by private healthcare contractor Medisure. The tapes also contained the records of 7,000 employees.
Boots said in a statement: "We would like to reassure our Boots Dental Plan customers that because of the type of data tape that was stolen and the way the information was stored it is highly unlikely that any personal data could be accessed or misused."
The Nottingham-based pharmacy chain added that Medisure has informed the Financial Services Authority and the Information Commissioner.
Medisure has also informed customers' banks as a precaution so that they can monitor affected accounts for any unusual activity.
The data tapes have been described as "technically complicated" and only accessible with specialist IT equipment and software.
Medisure could not be reached for comment at time of writing.