  We report the detection of pulse-to-pulse periodic intensity modulations, in
observations of recycled pulsars. Even though the detection of individual
pulses was generally not possible due to their low flux density and short
duration, through the accumulation of statistics over sequences of 10^5--10^6
pulses we were able to determine the presence and properties of the
pulse-to-pulse intensity variations of six pulsars. In most cases we found that
the modulation included a weak, broadly quasi-periodic component. For two
pulsars the sensitivity was high enough to ascertain that the modulation phase
apparently varies systematically across the profile, indicating that the
modulation appears as drifting subpulses. We detected brighter than average
individual pulses in several pulsars, with energies up to 2--7 times higher
than the mean, similar to results from normal pulsars. We were sensitive to
giant pulses of a rate of occurrence equal to (and in many instances much lower
than) that of PSR B1937+21 at 1400 MHz (~30 times lower than at 430 MHz), but
none were detected, indicating that the phenomenon is rare in recycled pulsars.
