  The nebular properties (electronic density, extinction, age, O/H abundances)
of HII regions found along the bars of the sample of barred spiral galaxies
studied by Martin & Friedli (1997) are examined. From line ratio diagnostic
diagrams, it is showed that regions located along the major axis of the bars
have a normal photoionization spectrum, that is, line ratios reproductible from
nebular conditions and ionizing star radiation field normally encountered in
extragalactic HII regions. There is an indication, however, that their degree
of ionization might be somewhat different. Another ionization mechanism
(high-velocity shocks or hard UV radiation) is clearly present for regions
found nearby the centers of the galaxies. The electronic density of the regions
along the bars is very close to that of disc regions ($<N_e > \sim 80
cm^{-3}$). On average, bar and disc regions have a similar visual extinction
($A_V \sim 1$ mag) with exceptions for some regions located near the bar dust
lanes of the earlier types of galaxies in our sample. Although the average
H$\alpha$ equivalent width of bar HII regions ($\sim$250 {\AA}) is half that of
disc regions, this disparity could be due to uncertainties in the galactic
continuum and does not translate into a significant age difference. The oxygen
abundance distribution was also investigated in the bar of these galaxies. The
O/H scatter was found to be very small (<0.1 dex) indicating that mixing of the
chemical composition by gas flows is very efficient in a barred structure.
