Mammographic x-ray spectra simulated by BEAMnrc/EGSnrc Monte Carlo code were qualitatively compared with the results obtained from the direct measurement using a cadmium telluride x-ray spectroscopy system and from the generation of IPEM report number 78. Generally, there is good agreement between the simulated and measured spectra, though there are slight differences at low energy in which the K-characteristic x-ray intensity is relatively higher for IPEM spectra. In addition, transmission curves were measured and simulated using a breast tissue-equivalent phantom (BR-12) as filtration. Comparison of the transmission curves shows good agreement. Moreover, the first half value layer (HVL) from direct measurement using ion chamber was consistent with the first HVL calculated by simulated spectra. Therefore, Monte Carlo may be used as an alternative tool for obtaining x-ray spectra when direct measurement is not available.