We have measured rotational velocities and oxygen abundances in 29 blu
e horizontal-branch (BHB) stars in M13, 22 in M3, and 16 in NGC 288 fr
om high-resolution spectra of the O I triplet at 7771-7775 Angstrom. H
ere we outline the behavior of rotation and oxygen line strength with
stellar effective temperature T-eff within each cluster and compare th
e average values of each from cluster to cluster. The mean strength of
the oxygen lines is greatest in NGC 288 and weakest in M3. Within eac
h cluster, the oxygen abundances are nearly constant among stars of a
given T-eff but may decrease with increasing T-eff. Among the BHB star
s cooler than 10,000 K, there is no sign of the counterparts to the su
per-oxygen-poor giants which dominate the bright end of the giant bran
ch in M13. The stars hotter than T-eff = 11,500 K show no oxygen lines
at all. While these faint blue stars have poorly exposed spectra and
may be hot enough to ionize oxygen, the abruptness of the disappearanc
e of the O I lines suggests that either the oxygen abundances are trul
y low or diffusion sets in abruptly at this color. No star in any clus
ter rotates more rapidly than 40 km s(-1). Thus [upsilon sin i] is muc
h lower in BHBs than in the superficially similar Population I B8 V-A7
V main-sequence stars. In M13, there is no obvious dependence of upsi
lon sin i on horizontal-branch (HE) color. The distribution of upsilon
sin i values in that cluster can be matched only with a bimodal or ot
herwise non-Gaussian distribution of upsilon values. Rotational veloci
ties are largest in M13, where six stars have v sin i greater than or
equal to 30 km s(-1), and are much smaller in M3 and NGC 288, with non
e at this level. Since both M13 and NGC 288 have very blue HBs, this i
ndicates that rotation and oxygen abundance are not enough by themselv
es to determine HE color, either alone or together; another factor suc
h as age must also be at work. Thus, the ''second-parameter'' problem
involves more than one such parameter, whose relative influence varies
among clusters.