Sliders started off as a FoxTV show. Half way through the first season it was cancelled, then resurrected and ran for three full seasons. Then Fox cancelled it again. It was then resurrected for a second time by the SCI FI channel, who made a further two seasons. During its five-year run Sliders also suffered the loss of four major cast members.
It was then cancelled again and Sliders will not be renewed for a sixth season. According to a SCI FI spokesperson, the channel thinks highly of Sliders, but feels the show has simply run its course. There is rumour of a Sliders Movie though.
I think that in many places only the FoxTV, first three seasons have ever been aired. Sky One has shown them all, and I thought that BBC2 had also. If you can get SCI FI they have just started from the very beginning again.