Absbnet We obtain the accurate wavefunctions and energies for n"S and n' .' P states of He for n<5 by variational configuration calculation with Bspline basis functions. The accurate wavefunctions have been used to calculate oscillator strengths for the transitions mS+rP, m, n<5 in He. ?e results offvalues are accurate to within 0.01 per cent or better.The error estimate is based on the numerical convergence as the number of the angular partial waves of the employed wavefunctions is increased, and on the agreement between the results obtained using the dipole length and velocity formula. The accuracy of our results does not deteriorate with increasing principal quantum number. The accuracy of ow results is better than the previous highly accurate calculated results of Schiff er U/ and &no and Hattori. Our results also agree with some recent accurate experimental results. Therefore, our results can be regarded as being as reliable as those of Kono and Hattori at least, which are likely to be the most accurate theoretical results. Some radial expectation values are also calculated to give so" indication of the accuracy of the wavefunctions. (1971) and Kono and Hattori (1984) have given accuratefvalues with m, n 6 5 and m, n < 9 respectively. They used variationally optimized wavefunctions containing explicitly the coordinate rlz, and obtained an estimate accuracy of 1 per cent to 0.1 per cent or better for the large majority of the transitions. With double groups of Hylleraas hasis functions, Kono and Hattori (1984) have given a remarkable improvement overfvalues for transitions involving higher-lying excited states, which were given by Schiff et al (1971). However, it is desirable to improve the previous results when transitions involve higher-lying excited states. 1984) in helium and helium-like ions. For n~'l~S-n'.~P transitions in He, Schiff et alGreen et al (1965, 1966) and Davis and Chung (1982) have calculatedfvalues for mS-nP transitions in He in the configuration-interaction calculation. But, their accuracies are poorer than what Schiff et aZ (1971) and Kono and Hattori (1984) gave. It seems t

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