Block Listing Return

BLOCK LISTING RETURN                              

Name of applicant: MICROGEN PLC

Name of scheme: MICROGEN PLC 1997 AND 1999 EXECUTIVE SHARE OPTION SCHEME

MICROGEN PLC 1996 SAVINGS RELATED SHARE OPTION SCHEME

Period of return: From: 9 MARCH 2005 To: 31 MARCH 2006

Balance under scheme from previous return:

MICROGEN PLC 1997 AND 1999 EXECUTIVE SHARE OPTION SCHEME - 800,000 ORDINARY
SHARES OF 5P EACH

MICROGEN PLC 1996 SAVINGS RELATED SHARE OPTION SCHEME - 200,000 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: N/A

Number of securities issued/allotted under

scheme during period:

MICROGEN PLC 1997 AND 1999 EXECUTIVE SHARE OPTION SCHEME - 96,000 ORDINARY
SHARES OF 5P EACH

MICROGEN PLC 1996 SAVINGS RELATED SHARE OPTION SCHEME - 112,147 ORDINARY SHARES
OF 5P EACH

Balance under scheme not yet issued/allotted

at end of period

MICROGEN PLC 1997 AND 1999 EXECUTIVE SHARE OPTION SCHEME - 704,000 ORDINARY
SHARES OF 5P EACH

MICROGEN PLC 1996 SAVINGS RELATED SHARE OPTION SCHEME - 87,853 ORDINARY SHARES
OF 5P EACH

Number and class of securities originally

listed and the date of admission

MICROGEN PLC 1997 AND 1999 EXECUTIVE SHARE OPTION SCHEME - 800,000 ORDINARY
SHARES OF 5P EACH

MICROGEN PLC 1996 SAVINGS RELATED SHARE OPTION SCHEME - 200,000 ORDINARY SHARES
OF 5P EACH

Total number of securities in issue at the end

of the period

102,535,714 ORDINARY SHARES OF 5P EACH

Name of contact: G.E. LIDDLE

Address of contact: FLEET HOUSE, 3 FLEETWOOD PARK, BARLEY WAY, FLEET,
HAMPSHIRE, GU51 2QJ

Telephone number of contact: 01252 772 326