Transparent glasses with densities greater than 8 g/mL, which are resistant to nuclear radiation damage and can serve as a host for rare‐earth scintillators, are being developed. Glasses in the PbO–Bi2O3 system are known to have some of the highest densities yet reported. In this study, a thorough reexamination of these glasses has been performed to examine their optical‐transmission windows and densities. The observed glass‐forming range found in this work agrees well with that reported in the literature. A minimum of ≅ 10 mol% B2O3 was required in some cases to vitrify the compositions. Glasses were examined in which the PbO:Bi2O3 ratios ranged from 10:90 to 90:10 with a maximum total B2O3 content of ≅50 mol%. Glasses with higher B2O3 contents were not examined because of the rapidly decreasing density with increasing B2O3 content. The densities of the glasses ranged from a low of 6.0 g/mL to a high of 8.1 g/mL. The highest densities were observed for glasses with the greatest PbO content. Ultraviolet/visible and infrared spectra were recorded for these glasses. The transmission window lies between ≅430 and 3850 nm. A systematic increase in the cutoff wavelength was found to occur with an increase in the density. Water‐absorption peaks were found in the infrared spectra at ≅3000 nm.