Offer Document Posted

NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION DIRECTLY OR INDIRECTLY IN OR INTO
ANY RESTRICTED JURISDICTION INCLUDING THE US, CANADA, AUSTRALIA OR JAPAN.

FOR IMMEDIATE RELEASE

18 August 2004

Microgen plc

Posting of Offer Document, Listing Particulars and Circular

Further to the announcement dated 13 August 2004 regarding the recommended
offer to be made by UBS Investment Bank on behalf of Microgen plc ('Microgen')
for all of the ordinary share capital of AFA Systems plc ('AFA') and the
acquisition of the £1.5 million loan note issued by AFA (the 'Acquisition'),
the board of Microgen announces today that documents, including a shareholder
circular convening an extraordinary general meeting of Microgen at 10.30 am on
10 September 2004 to approve the Acquisition, and listing particulars
containing financial information relating to Microgen and AFA, have been posted
to Microgen shareholders.

In addition, AFA shareholders have been sent an offer document, containing
details of the offer, the accompanying form of acceptance and the listing
particulars containing financial information relating to Microgen and AFA. The
first closing date of the offer is 8 September 2004.

Copies of the above documents have been submitted to the UK Listing Authority
and will shortly be available for inspection at the UK Listing Authority's
Document Viewing Facility, which is situated at:

Financial Services Authority,

25 The North Colonnade,
Canary Wharf,

London E14 5HS

Tel: [phone]

(Documents will normally be available for inspection within six normal business
hours of this notice being given).

The above documents are also available for inspection at the offices of Clyde &
Co, situated at: 51 Eastcheap, London EC3M 1JP and also at the registered
office of Microgen at: 11 Park Street, Windsor, Berkshire SL4 1LU, during
normal business hours on any weekday (Saturdays, Sundays and public holidays
excepted) while the offer remains open for acceptance.

Enquiries:

Gerry Liddle, Company Secretary, Microgen plc

Tel: [phone]

Terms used in this announcement shall have the same meaning as those in the
Offer Document, Listing Particulars and Circular.

UBS is acting exclusively for Microgen in connection with the Acquisition and
no one else and will not be responsible to anyone other than Microgen for
providing the protections afforded to clients of UBS, or for providing advice
in relation to the Acquisition.