Why the Buddha didn't originally allow ordination of women Is it true that the Buddha didn't allow women in the Sangha? If this is true then why is that?
Interesting, this is the first question answered in this month's Buddhism.SE Book-of-the-Month Women in Buddhism - Questions &amp; Answers.


  It was the right time for Maha Pajapati (the Buddha's step mother) to consider following
  the teaching and the practice of the Buddha seriously. But
  when she approached and asked for permission the Buddha
  simply said, “Please do not ask so.” The Tripitaka, which
  is the most important primary source, did not provide any
  reason for not allowing women to join the Order.


Maha Pajapati and 500 other women shaved their heads, donned yellow robes, and walked to where the Buddha was. Ananda went to the Buddha on their behalf to ask for their permission to join the sangha, but the Buddha's response was "“Ananda, please do not ask so.”.

Some of the considerations and concerns that might have been present include the fact that:


  According to
  Indian social mores, to lead a religious life is not the path
  for women. ibid


There may also have been practical concerns as these women had lived in comfort before and the reality of living a reclusive life outdoors might be difficult. The current sangha did not have enough teachers who would have been suitable to teach this large group of women. There could have been criticism that having women join the sangha was breaking up families. These may have been some of the reasons behind the Buddha's hesitation to allow women to join the sangha.

When Ananda asked the Buddha if women were capable of attaining spiritual enlightenment; the Buddha's answer was yes. The book notes:


  We have to mark this statement, as this is the first time
  in the history of religion that a religious leader declared
  openly that men and women are equal on spiritual grounds.
  Previously in the Hindu context, the Vedas, the most sacred
  religious texts, were available only to men. Buddhism has
  transcended race, nation, caste and gender differences to 
  declare that the highest spiritual achievement transcends
  obstacles or discrimination of gender. With this important
  reason, the Buddha allowed women to join his Order. ibid


So while women weren't allowed to join the sangha immediately, eventually they were.