Isotope dilution concentration determinations accurate to ~1% for Rb and Sr, and 0.5% for Sm and Nd. Total procedural blanks averaged not, vert, similar1 ng for Pb and Sr, and 100 pg for Nd, during study period. Measured 87Sr/86Sr ratios were analyzed using four-collector static mode measurements. Thirty measurements of SRM-987 during the study period yielded mean 87Sr/86Sr=0.71032±2. Measured 143Nd/144Nd normalized to 146Nd/144Nd=0.7219. Analyses were dynamic mode, three-collector measurements. Thirty-three measurements of the La Jolla Nd standard during the study period yielded a mean 143Nd/144Nd=0.511838±8 (2sigma mean). e-Nd values calculated using a present day 143Nd/144Nd(CHUR)=0.512638. Pb isotopic analyses were four-collector static mode measurements. Sixteen measurements of SRM-981 during the study period yielded 208Pb/204Pb=36.56± 0.03, 207Pb/204Pb=15.449±0.008, 206Pb/204Pb=16.905±0.007 (2sigma mean). Measured Pb isotope ratios were corrected to SRM-981 values (208Pb/204Pb=36.721, 207Pb/204Pb=15.491, 206Pb/204Pb=16.937).