  Extensive photometric and spectroscopic observations of SN1994aj until 540d
after maximum light have been obtained. The photometry around maximum suggests
that the SN belongs to the Type II Linear class, with a peak absolute magnitude
of Mv ~ -17.8 (assuming Ho=75 km/s/Mpc). The spectra of SN1994aj were unusual
with the presence of a narrow line with a P-Cygni profile on the top of the
broad Balmer line emission. This narrow feature is attributed to the presence
of a dense superwind surrounding the SN. At 100-120 days after maximum light
the SN ejecta starts to interact with this CSM. The SN luminosity decline rates
slowed down (gamma_R=0.46 mag/100d), becoming less steep than the average late
luminosity decline of normal SNII (~1 mag/100d). This dense (Mdot/u_w ~ 10^15
g/cm) wind was confined to a short distance from the progenitor (R_out ~
5x10^16 cm), and results from a very strong mass loss episode (Mdot = 10^-3
Msun/yr), which terminated shortly before explosion (~5-10 yr).
