<qa>  What is the risk reduction to 60 for indolent lymphomas?The improvement expected by the new maintenance with rituximab for progression free survival can be expressed by reduction of relative risk rr. Since a risk reduction to 60 was observed for indolent lymphomas by interferon maintenance, this seems to be a clinical relevant improvement for the new maintenance therapy. For a working significance level alpha0.05 and a power of 95 the number of events relapse or death necessary for a two sided fixed sample trial is about 200. During this study the progression free survival in patients after successful initial therapy will be monitored by an equivalent restricted sequential procedure with a maximum number of 240 observation. 