I have recently noticed on my Saab 9-5 2.3ltr Turbo 1998 Model.
Occasionally white smoke seems to be coming out of the exhaust when in
first or second gear. This is not very often,even after the car is
warmed up.
What is the possible problem and how to fix it?

I'm fond of my SAAB 9000.  White smoke probably means uncombusted
gasoline.  I'd certainly take it in for a tune-up.

Have you noticed poor mileage of late?

regards, mathtalk-ga

A worse case scenario might be a headgasket problem, cracked or warped
head, intake manifold or gasket, or cracked block that is allowing
coolant (radiator water) to mix with your oil. This can cause white
smoke like the kind you mentioned. One quick way to check to see if
you have a headgasket problem it to look at the end of your dipstick.
If you have *ANY* water bubbled up there (even one drop) or a little
trace of a grayish white goo you probably have water in your cylinders
that's causing the smoke symptoms you are experiencing.

tutuzdad-ga

White smoke, as tutuzdad points out, is usually caused by water in the
gas or engine. I don't think it'd be a blown gasket or cracked block
though, because that could let oil in, and that would make black
smoke, although maybe it was such that it only allowed water in? My
guess (it's only a guess) is that water got in your system somehow.

White smoke usually means that there's a new Pope.

A Swedish pope?

Sven Goren Erikson?

Good one Bryan!. A relly of mine had a SAAB. cost them $4,000 to
rebuild the gearbox. Had nothing but trouble. Got rid of the SAAB, and
divorced. TROUBLE TROUBLE TROUBLE.

How many miles are on your car?

You could try this, have someone follow you, get your car up to 60
miles an hour, take your foot off the gas, let the car coast IN FORTH
GEAR until you hit about 20 miles an hour.  Leave it in forth gear and
hit the gas.  The car following you can tell you if it smokes.  If it
does the engine is, more than likely, burning oil from the rings.

When you start it in the morning does in smoke?  If it does the valve
guides are worn.

If your oil is milky looking then water is getting into the oil. 
Which could mean a blown head gasket.

Are you losing water from the radiator?

Has you car overheated lately? (blown head gasket or busted block, maybe)

I'm leaning to burning oil, from worn rings, if you're burning "water"
it's going to be using water and "smoking" in all gears, all the time.

I hope this helps.

By the way, if it's burning oil, it's no big deal.  Just keep it
topped off with oil and drive it.  If it's water, that's something
that will need to be fixed.

white smoke is most often a symptom of a leaking head gasket. that
being said, saabs are supposed to have very little problems with head
gaskets even on the turbo models. there is a test that can be
performed that involves using a tool to detect exhaust gases in the
cooling system. most rad shops have one. i would rather have a rad
shop do it than a garage because a garage would benefit from getting
the resulting repair work while a rad shop does not. the tool is about
40.00 so you can actually buy it yourself from a parts jobber or
snap-on.

before you even bother, take it out for a good highway run to make
sure that the exhaust system is well warmed up and see if you can get
any white smoke.

btw, when it's a coolant leak the exhaust will smell sweet.