We present the first comparison of profiles of H et He resonance lines observed by SUMER with theoretical profiles computed with our non-LTE radiative transfer code .
We use the H i Lyman \beta , H i Lyman \epsilon , and He i \lambda 584 Å lines .
Our code allows us to obtain the plasma parameters in prominences in conjunction with a multi-line , multi-element set of observations .
The plasma temperature in the prominence core is \sim 8600 K and the pressure is 0.03 dyn cm ^ { -2 } .
The Ly \beta line is formed in a higher temperature region ( more than 11 000 K ) .