  A two-step, two-color laser spectroscopy technique has been used to measure
the hyperfine splittings of the $8p$ excited states in $^{203}$Tl and
$^{205}$Tl, as well as the $7s - 8p$ transition isotope shifts. For the case of
the $8p_{3/2}$ state, our results show a hyperfine anomaly consistent with our
recent measurements of other hyperfine splittings, and in disagreement with
older results for this state. Our measurement of the $8p_{1/2}$ isotope shift
is also in disagreement with earlier work. In this series of experiments, a UV
laser was locked to the first-step transition and directed through a heated
vapor cell, while a second spatially overlapping red laser was scanned across
the two second-step transitions. To facilitate accurate frequency calibration,
radio-frequency modulation of the second-step laser was used to create
sidebands in the Doppler-free absorption spectrum.
