Dislocation generation associated with oxide precipitates in heavily boron-doped Czochralski silicon wafers with resistivities of 9, 18, and 40 m Omega cm has been studied following prolonged isothermal annealing from 800 to 1000 degrees C. Transmission electron microscopy observations revealed (i) the critical precipitate size for punched-out dislocations to form in 9 and 18 mn cm wafers was smaller than 40 nm in 9 and 18 m Omega cm wafers, while larger than 55 nm in 40 m Omega cm samples; (ii) the precipitate density was higher than 10(12) cm(-3) in 9 and 18 m Omega cm wafers, and below 10(11) cm(-3) in 40 m Omega cm wafers annealed at 800 and 900 degrees C, respectively. The strain around a precipitate was estimated and it was concluded that the higher supersaturation of silicon interstitials in the 9 and 18 m Omega cm wafers was due to the higher precipitate density, which in turn was likely to be the main cause of the reduction in critical precipitate size.