I have two black wires, one red, one wihite out of the box. I have connected the two blacks with the black fixture, and white with the white fixture wires. The red is not connected. The light (florescent U-tube light) comes on, but stays on, regardless of the switch being in the on or off position, what have I done wrong? Please help

More than likely you have just wired around the switch loop.

If a switch loop is present, you should find two cables in the ceiling. On will provide the power source and the other will provide the switch loop to the wall switch and back.

There is an alternative method of using a three wire to bring the power to the wall switch and then continue on to the device. In that case there would only one cable in the overhead.

Would you please pull the switch out and let me know what wires are connected to the switch.

Sounds like the red was being used as the switched wire.

How was the old fixture hooked up?

Sounds like the red was being used as the switched wire.

How was the old fixture hooked up?

I didn't check that in my haste to connect the new one

On one of the white cables in the ceiling, is there black tape on it or any color tape? If there is, then do not follow the procedure given below.

What I expect is that the Black carrying the source power was connected to the red.

The red is then connected to the Black on the light fixture.

The White with the source power connects to the White from the fixture.

Switches do not use Neutral, unless there is a pilot light on the switch.

Look again, unless you have individual wires pulled in conduit, you can't have two blacks, one red and one white. You can have two blacks, one red and two whites. Must have missed a white. Pull switch and tell us what wires are connected to switch.

Look again, unless you have individual wires pulled in conduit, you can't have two blacks, one red and one white. You can have two blacks, one red and two whites. Must have missed a white. Pull switch and tell us what wires are connected to switch.
You're right 2blacks, 2whites 1red.
One red, one black is connected to the switch

On one of the white cables in the ceiling, is there black tape on it or any color tape? If there is, then do not follow the procedure given below.

What I expect is that the Black carrying the source power was connected to the red.

The red is then connected to the Black on the light fixture.

The White with the source power connects to the White from the fixture.

Switches do not use Neutral, unless there is a pilot light on the switch.

There is no tape on the white or any wires. I have 2white, 2blacks, 1 red coming from the box, the light fixture has one white, one black.
The switch has a black and red going to it So what is the right connection that I should be doing?