More than 60 volunteer ambulance car drivers in mid and west Wales are starting a two-day "strike" in a dispute over mileage payments.
Drivers who use their own cars to transport patients to clinics and hospitals said 34p per mile was not enough to cover rising fuel costs.
It is thought hundreds of patients could be affected by the action.
The Welsh Ambulance Services NHS Trust said contingency plans were in place for as many patients as possible.
St John Cymru Wales, the Community Transport Association and Medical Services will be drafted in to help patients as much as possible, while drivers from other parts of Wales may help.
"They should stop wasting money on things that are not worth it and pay the people who deserve it"
The drivers, who cover Ceredigion, Pembrokeshire, Carmarthenshire and Swansea, claimed the decision to withdraw their services on Thursday and Friday was the last resort in a four-year battle.
Teifion Morris, from Cardigan, said he had been driving patients around the UK for more than 20 years, and now spent £100 on petrol every week.
He said: "We only get mileage [money]. I don't make a penny profit out of it.
"But it's coming to a point where I will be out of pocket, what with petrol costs rising.
"I give my time as it is and I give the depreciation of my car. My Vauxhall Astra is four years old and it's done 147,000 miles.
"Even if I wanted to change my car now I would get a pittance for it.
"They're treating us like monkeys and feeding us peanuts."
Mr Morris takes patients three times a week for dialysis in Aberystwyth, and he said they supported the action.
But some are worried how they will get their treatment.
"It's my health"
Ieuan Evans, who is retired, said: "We're behind it 100%. They should stop wasting money on things that are not worth it and pay the people who deserve it.
He said he had "no idea" how he would get to hospital on Friday for his next dialysis adding: "Of course I'm worried. If I don't go, that's it. It's my health."
Another driver, Pauline Rhodes of Aberporth, said: "We managed to get an agreement that the rate would go up to 38p a mile from next April but I have asked for an interim solution because of the recent tremendous increase in fuel prices."
A spokeswoman for the Welsh Ambulance Services NHS Trust said it had established one of the highest mileage allowances rates in the UK, from April 2008.
She added: "There are a number of contingency plans being put in place to make sure as many patients reach their treatment as possible on Thursday and Friday".
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~40~RS~)