>I am trying to set up the TMR1, on the '74, as a timer with a prescaler of 4
>that will trigger an interrupt on overflow.
>
>This is what I have setup so far:
>
>        Intcon  - GIE =1                ;global int's enabled
>                  the rest=0
>
>        PIE1    - TMR1IE =1             ;enable TMR1IF interrupt
>                  the rest=0
>
>        T1CON   - TMR1ON=1              ;starts timer
>                  T1CKPS0=0             ;sets prescaler
>                  T1CKPS0=1             ;  "  "
>                  the rest=0

PEIE needs to be set - as already stated by Andrew Warren

TMR1CS needs to be 0 (internal clock)
T1OSCEN could be turned off for good measure as well

Are you remembering to initialise the TMR1H and TMR1L registers - as well as
re-loading them when entering the interrupt service routine?

Also, did you clear PIR1  - TMR1IF before you enabled the interrupt for the
first time (and does your interrupt service routine clear it again?)

I did all that, and mine is quite happily giving me a 2mS interrupt...

Jim