A key player, Saudi oil minister Ali Naimi, is not attending the meeting, which leaves only a monitoring group lacking the power to decide on any production cuts.
The emergency discussions are more likely to lead to recommendations for action or an emergency meeting of all 11 Opec ministers.
On arrival in Vienna, the delegates - from Iran, Nigeria, and Kuwait - as well as Opec's secretary general Rilwanu Lukman declined to reveal a precise agenda, but prices are expected to be their main concern.
The price of oil plunged from $18 per barrel from $14 per barrel last November when, under pressure from Saudi oil minister Ali Naimi, Opec decided to raise output by 10%.
The move leaves oil prices $10 per barrel lower than last January, when markets were firm.
Expectations for massive growth in the international demand for crude oil were shattered by the economic troubles in Asia.
Analysts have criticised Opec for pumping too much oil in a market that has been severely weakened by the Asian crisis.
Quota cheating also contributes to excess output - believed to be as much as 3m barrels per day.
Opec is reviewing the problem of overproduction but has not yet made plans to limit supply.
Market analysts have said that raising expectations of a production cut without actually making any concrete decisions could weaken the market further.
Some analysts have suggested that Saudi Arabia, which pushed the controversial plans to raise output, could help solve the problem by quietly and unilaterally deciding to pump less oil.
OPEC concerned over oil price collapse
(26 Jan 98 | World)
OPEC to pump more oil
(29 Nov 97 | Business)
The BBC is not responsible for the content of external internet sites.
Prescott rejects £1.2bn Chunnel link rescue
South Korea and banks agree revised debt terms
Consumer confidence slipping
Race for Japan's finance ministry hots up
Industry sees red over tax plans
Fat cats under threat
Japan asked to remove business regulations
(From Despatches)
Chips are down for Japanese giant NEC
Record fine for insurer over pensions review
Browser wars cost Netscape dear
Northern Rock squeezes out £2m charity boost
Mars licks Unilever in ice-cream war
Black & Decker slashes 3,000 jobs worldwide
Three-way bid battle looms over Energy Group
Appeal to spare company cars
Accounts probe slashes Powerscreen shares in half
Bangladesh exploits gas finds