Hipparcos photometric data for the massive O-type binary UW CMa were analysed within the framework of the Roche model .
Photometric solutions were obtained for five mass ratios in the q = M _ { 2 } / M _ { 1 } = 0.5 - 1.5 range .
The system is found to be in a contact configuration .
Independently of q , the best-fitting model solutions correspond to the orbital inclination i \sim 71 ^ { \circ } and the temperature of the secondary component T _ { 2 } \sim 33500 K , at the fixed temperature of the primary T _ { 1 } = 33750 K .
Considering that the spectrum of the secondary is very weak , photometric solutions corresponding to the contact configuration favor the mass ratio q smaller than unity ( in which case the luminosity of the secondary is smaller than that of the primary ) .
The absolute parameters of the system are estimated for different values of the mass ratio .