Junior doctors' dispute: What next?
The action came after the British Medical Association (BMA) and the government failed to reach agreement on a proposed new contract for junior doctors.
The BMA, which is concerned about pay for weekend working, career progression and safeguards to protect doctors from being overworked, said the strike had sent a "clear message" to the government.
However, Health Secretary Jeremy Hunt described the walkout as "completely unnecessary" and urged junior doctors to return to the negotiating table.
The last time both sides met formally was on Friday, but negotiations were put on hold while the strike took place.
Officials from Acas said they would hold discussions with both sides on Thursday and Friday, although government sources said they were still prepared to impose the contract if the deadlock could not be broken.