Castlerigg Master Investments Ltd.

Castlerigg Master Investments Ltd.

00 Xxxx 00xx Xx

00xx Xxxxx

Xxx Xxxx, XX 00000

pSivida Limited

Xxxxx 00, XXX Xxxxxx

00 Xxx Xxxxxxxxx

Xxxxx, XX 0000

Xxxxxxxxx

Re: Extension of Dates in Second Amendment Agreement

Reference is hereby made to that certain Second Amendment Agreement, dated as of December 29, 2006 ("Agreement"), by and between pSivida Limited (the "Company") and Castlerigg Master Investments Ltd.

Section 2(d) of the Agreement is hereby amended by changing the date in clause (i) thereof from "5:00 p.m. prevailing Boston, Massachusetts time on Saturday, March 31, 2007" to "5:00 p.m. prevailing Boston, Massachusetts time on April 2, 2007". Section 8 of the Agreement is hereby amended by changing the date therein from "April 2, 2007" to "April 7, 2007".

The other terms and conditions in the Agreement shall not be amended hereby and shall remain in full force and effect.

	Very truly yours,
	CASTLERIGG MASTER INVESTMENTS LTD.
	By: Xxxxxxx Asset Management Corp.
	By:	/s/ Xxxxxxx X’Xxxxx
		Name: Xxxxxxx X’Xxxxx
		Title: Chief Financial Officer

Agreed to and Accepted by:

PSIVIDA LIMITED

By:		/s/ Xxxxxxx X. Xxxx
		Name: Xxxxxxx X. Xxxx
		Title: V.P. and CFO