Why you should travel by train in Vietnam...
You'd be crazy not to.  Vietnam's air-conditioned trains are safe, comfortable & inexpensive, the ideal way for independent travellers to get around and see Vietnam at ground level.  The train journeys are an experience in themselves, and become an integral part of your visit to Vietnam.  You might even meet some Vietnamese people.  Inexperienced travellers often mistakenly think they'll save time by using internal flights - in fact, an overnight train ride from Hanoi to Hué or Danang is not only far more of an experience (and cheaper) than a flight, the train actually saves time compared to flying, because the train leaves Hanoi city centre in the evening and arrives in Hué city centre next morning.  Flying takes 4 or 5 hours out of your sightseeing day in getting to a remote airport, checking in, taking the flight itself, collecting your bags and getting back into the city centre.  And the sleeper trains saves a hotel bill, too.  And what's the rush anyway?
   

The Reunification Express?
Trains between Hanoi & Saigon are sometimes referred to as the 'Reunification Express' by guide books or tourist agencies.  However, there are now many trains on this route and no single train officially carries this name.

You'll see some amazing scenery from the train between Hanoi and Saigon.  Easily the best section is between Hué and Danang over the Hai Van Pass, where the train runs along the coast past bays and islands and through the hills.  The train travels at low speed up the fierce gradients, with an assisting locomotive at the rear and people sitting on the roof!  See the video above and the pictures below.  For a good video montage of a Saigon-Hanoi train journey click here.

Hanoi - Hue - Danang - Saigon
Over the last decade the Hanoi-Saigon train service has been steadily improving and a whole range of daily air-conditioned trains now link Hanoi, Hue, Danang, Nha Trang & Saigon (HCMC).  Here are the principal trains, all running daily.  Look for the 'SE' numbered trains, as these are the best.  The 'TN' trains are slower and older.  There are additional trains at peak times, such as the Tet holiday period.  You can check train times at the Vietnamese Railways website, www.vr.com.vn.

Trains SE1-SE6 have air-con soft sleepers (4-berth), air-con hard sleepers (6-berth), air-con soft seats & air-con restaurant car.
Trains SE7-SE8 have air-con hard sleepers (6-berth), air-con soft seats & air-con restaurant car.  No soft sleepers.  Note that the timetable for SE7/SE8 may have changed by several hours in early 2010, information is not available.

Livitrans private tourist sleeping-cars:  Trains SE1 & SE2 now have a new tourist sleeping-car attached between Hanoi, Hue & Danang run by private company Livitrans.  It has 4-berth sleeper compartments of a much higher standard than the regular Vietnamese Railways ones, and fares only a bit higher.  See the photos below & see www.livitrans.com for fares & online booking.

Trains TN1 & TN2 have ordinary non-aircon hard sleepers (6-berth) & hard seats only.
Hanoi to Saigon is 1,726km, about 1,070 miles.

How to buy tickets...
Do I need a reservation?  Can I stop off along the way?  Can hop on and off?
Yes, yes, and no...  All trains require a reservation, so you need a specific ticket/reservation for each individual train journey you make.  If you want to travel from Saigon to Hanoi (or vice versa) stopping off on the way, this is not a problem, but you will need to book it as a series of separate journeys, with a separate ticket for each leg either bought in advance or bought as you go along.  You cannot buy an open ticket and hop on and off trains without a reservation.

Buy tickets by email through a travel agency...
Reliable Vietnamese travel agencies who will book train tickets by email include VietnamCruiseDeals ( www.vietnamcruisedeals.com, Vietnamstay (www.vietnamstay.com) Saigon Hotel (www.saigonhotel.com).

EXPRESS TRAINS: HA NOI - LAO CAI
First Class cabin: 25 US$/one way
Economy Class: 20 US$/ one way

EXPRESS TRAINS: HA NOI - HUE
First Class cabin: 39 US$/one way
Economy Class: 34 US$/ one way

Night Trains to Sapa: Fanxipan train, Tulico train, King express, Pumpkin train, Livitrans express, Cao Son train