There is no easy answer to this as it depends on many factors including you risk profile and your current financial position. If you are unsure, as I think you are then you should seek the advice from an Independent Financial Advisor (IFA). That said ISAs are not an investment, they are a wrapper. You can only take one ISA out in any one financial year. If you mean you wish to buy a lump sum �7200 equity based ISA for 2008/2009 and hold it for 5 years then this may not be the best move. Any equity based investment should be viewed medium to long term, say 5 to 10 years. As to when to invest it is more of case of 'time in' and not 'timing'. A drip fead approach to take advantage of what is called pound cost averaging (buying less unit/shares etc when the price is high and buying more when the price is low) I would consider a sensible approach and in this FY you could invest �900 each month from now until Mar 09. It is very difficult to fully answer your question without knowing your personal circumsatnces. In summary if I was you I would seek the expert advise of an IFA you can find them in your local Yellow Pages or from the IFA Association. Over to you and all the best.