Block Listing Return

MICROGEN PLC

27 SEPTEMBER 2011

BLOCK LISTING RETURN

Name of applicant: MICROGEN PLC

Name of scheme: MICROGEN PLC PERFORMANCE SHARE PLAN 2006

MICROGEN PLC COMPANY SHARE OPTION PLAN 2006

Period of return: From: 25 MARCH 2011 To: 24 SEPTEMBER 2011

Balance under scheme from previous return:

MICROGEN PLC PERFORMANCE SHARE PLAN 2006 - 411,233 ORDINARY SHARES OF 5P EACH

MICROGEN PLC COMPANY SHARE OPTION PLAN 2006 - 261,655 ORDINARY SHARES OF 5P EACH

The amount by which the block scheme has been increased, if the scheme has been increased since the date of the last return:

MICROGEN PLC PERFORMANCE SHARE PLAN 2006 - 0 ORDINARY SHARES OF 5P EACH

MICROGEN PLC COMPANY SHARE OPTION PLAN 2006 - 0 ORDINARY SHARES OF 5P EACH

Number of securities issued/allotted under scheme during period:

MICROGEN PLC PERFORMANCE SHARE PLAN 2006 - 0 ORDINARY SHARES OF 5P EACH

MICROGEN PLC COMPANY SHARE OPTION PLAN 2006 -139,168 ORDINARY SHARES OF 5P EACH

Balance under scheme not yet issued/allotted at end of period

MICROGEN PLC PERFORMANCE SHARE PLAN 2006 - 411,233 ORDINARY SHARES OF 5P EACH

MICROGEN PLC COMPANY SHARE OPTION PLAN 2006 - 122,487 ORDINARY SHARES OF 5P EACH

Number and class of securities originally listed and the date of admission

MICROGEN PLC PERFORMANCE SHARE PLAN 2006 - 127,460 ORDINARY SHARES OF 5P EACH - 7 SEPTEMBER 2009

MICROGEN PLC COMPANY SHARE OPTION PLAN 2006 - 142,001 ORDINARY SHARES OF 5P EACH - 7 SEPTEMBER 2009

MICROGEN PLC PERFORMANCE SHARE PLAN 2006 - 650,000 ORDINARY SHARES OF 5P EACH - 24 SEPTEMBER 2010

MICROGEN PLC COMPANY SHARE OPTION PLAN 2006 - 350,000 ORDINARY SHARES OF 5P EACH - 24 SEPTEMBER 2010

Total number of securities in issue at the end of the period

81,316,094 ORDINARY SHARES OF 5P EACH

Name of contact: PHILIP WOOD, DIRECTOR

Address of contact: OLD CHANGE HOUSE, 128 QUEEN VICTORIA STREET, LONDON, EC4V 4BJ

Telephone number of contact: 020 7496 8100

www.microgen.com