widths of the [H$\alpha$]{} and [H$\beta$]{} lines. While a number of studies have investigated the relative differences in the profiles of the [H$\alpha$]{} and [H$\beta$]{} lines (e.g., Osterbrock & Shuder 1982; Shuder 1982, 1984; Crenshaw 1986; Stirpe 1991; Kollatschny 2003), ours considers by far the largest and most homogeneous sample to date. Consistent with previous studies, we find that [H$\beta$]{} generally has a slightly broader profile than [H$\alpha$]{}. We measure $\langle$[$\mathrm{FWHM}_\mathrm{H{\beta}}$]{}/[$\mathrm{FWHM}_\mathrm{H{\alpha}}$]{}$\rangle = 1.17$ with an error in the mean of 0.01 and an rms of 0.2. This value is, in fact, identical to the average value found by Osterbrock & Shuder (1982), but considering our order-of-magnitude increase in sample size this agreement must be fortuitous. The relative profile of [H$\alpha$]{} and [H$\beta$]{} depends on both the kinematic and ionization structure of the BLR, since [H$\beta$]{} is emitted preferentially in regions of higher density and/or higher ionization parameter than [H$\alpha$]{}(e.g. Osterbrock 1989). The tendency for the [H$\beta$]{} profile to be broader than [H$\alpha$]{} is not surprising if the density or ionization parameter of the BLR increases with decreasing radii.

Further insights into the physical conditions of the BLR may be gleaned from the Balmer decrements that come as a by-product of 