Context :

Aims : We investigate the binary star T Tauri South , presenting the orbital parameters of the two components and their individual masses .

Methods : We combined astrometric positions from the literature with previously unpublished VLT observations .
Model fits yield the orbital elements of T Tau Sa and Sb .
We use T Tau N as an astrometric reference to derive an estimate for the mass ratio of Sa and Sb .

Results : Although most of the orbital parameters are not well constrained , it is unlikely that T Tau Sb is on a highly elliptical orbit or escaping from the system .
The total mass of T Tau S is rather well constrained to 3.0 ^ { +0.15 } _ { -0.24 } M _ { \odot } .
The mass ratio Sb : Sa is about 0.4 , corresponding to individual masses of M _ { Sa } = 2.1 \pm 0.2 M _ { \odot } and M _ { Sb } = 0.8 \pm 0.1 M _ { \odot } .
This confirms that the infrared companion in the T Tauri system is a pair of young stars obscured by circumstellar material .

Conclusions :