Multiband spectra of blazars, showing the distribution of flux vs. the rest‐frame frequency. Squares: Simultaneous observations with ASCA (although for radio data they include quasi‐simultaneous observations). Dashed line: Polynomial fit to the spectrum. X‐ray spectra are corrected for absorption using the Galactic column density. Hatched region in QHBs corresponds to the estimated range of ν_SSC and L_SSC. For 3C 279, we plot the ASCA as well as the Ginga X‐ray spectra; squares: observations contemporaneous with the plotted Ginga data (see also Maraschi et al. 1994b). The data from the radio‐to‐optical bands were mainly taken from the NED database. The radio data were also taken from the UMRAO database and H. Teräsranta & M. Tornikoski (1996, private communication). We also used data from Bersanelli et al. (1992; optical), Pian & Treves (1993; UV), Falomo, Scarpa, & Bersanelli (1994; optical), Giommi, Ansari, & Micol (1995; radio to X‐ray), Impey et al. (1988; IR), Neugebauer et al. (1986; IR), McNaron‐Brown et al. (1995; OSSE, COMPTEL, EGRET), Bloom et al. (1994; radio, millimeter, IR), and Fichtel et al. (1994; EGRET upper limit). Additional data for each object were taken from H0323+022 (Feigelson et al. 1986; Jannuzi et al. 1993; Falomo et al. 1993), H0414+009 (McHardy et al. 1992), PKS 2155−304 (Vestrand, Stacy, & Sreekumar 1995), Mrk 421 (Macomb et al. 1995), Mrk 501 (Kataoka et al. 1998), H1426+428 (Remillard et al. 1989), OJ 287 (Landau 1983; Idesawa et al. 1997; Shrader, Hartman, & Webb 1996), AO 0235+164 (Madejski et al. 1996), PKS 0735+178 (Nolan et al. 1996), 0716+714 (Lin et al. 1995), 3C 273 (von Montigny et al. 1993, 1997; ROSAT: MPE Annual Report 1993), 3C 279 (Hartman et al. 1996), PKS 0208−512 (Veron‐Cetty & Veron 1993; Blom et al. 1995; Stacy et al. 1996), PKS 0528+134 (Rieke et al. 1982; Collmar et al. 1998), and 4C 38.41 (Landau 1986; Mattox et al. 1993).