FORTUNE — Venture capital firm Andreessen Horowitz is in the process of raising around $1.5 billion for its fourth fund, Fortune has learned.

This would be very similar in structure to the $1.5 billion fund raised by Andreessen Horowitz in early 2012, which included a $900 million fund for early-stage investments and a $600 million “parallel fund” for larger opportunities. It is expected that the new effort would have around $1 billion for the general fund and $500 million for the parallel fund, although that may change before a final close is held later this quarter.

Sources say that the fund is already oversubscribed, and is unlikely to accept many new limited partners (if any at all).

Andreessen Horowitz portfolio companies include AirBNB, Box, DataGravity, Lyft and Pinterest. Past investments have included Facebook FB and Skype (acquired by Microsoft).

Andreessen Horowitz spokeswoman Margit Wennmachers declined to comment.

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