  Our goal was to improve the fundamental parameters of the massive close
double-lined eclipsing B2.5V+B2.5V binary CV Velorum.We gathered new
high-resolution echelle spectroscopy on 13 almost consecutive nights covering
essentially two orbits. We computed a simultaneous solution to all the
available high-quality radial-velocity and light data with the latest version
of the Wilson-Deviney code. We obtained the following values for the physical
parameters: $M_1 = 6.066(74) M_\odot$, $M_2 = 5.972(70) M_\odot$, $R_1 =
4.126(24) R_\odot$, $R_2 = 3.908(27) R_\odot$, $\log L_1 = 3.20(5) L_\odot$,
and $\log L_2 = 3.14(5) L_\odot$. The quoted errors contain a realistic
estimate of systematic uncertainties mainly stemming from the effective
temperature estimation. We derived abundances for both components and found
them to be compatible with those of B stars in the solar neighbourhood. We
discovered low-amplitude periodic line-profile variations with the orbital
frequency for both components. Their interpretation requires new data with a
longer time span. The primary rotates subsynchronously while the secondary's
$v\sin i$ and radius are compatible with synchronous rotation. Finally, we
provide an update of the empirical mass-luminosity relation for main-sequence B
stars which can be used for statistical predictions of masses or luminosities.
