Dixons Carphone and Capita are to be relegated from the FTSE 100 index after their shares fell sharply in the last quarter.
Their places will be taken by Scottish Mortgage Investment Trust and Rentokil.
The companies included in the UK's top tier index are reviewed every quarter and reshuffled according to their market capitalisation.
Dixons Carphone shares have lost nearly 20% of their value over the past six months.
The domestic appliance to mobile phone retailer reported increased profits at the end of last year but is battling higher import costs due to the weaker pound as well as increased competition from online retailers.
"Dixons Carphone's share price has dropped off of late as a result of increasing competition within the sector, particularly from the likes of Amazon," said Helal Miah, an analyst at The Share Centre.
Shares in outsourcing giant Capita fell after a profits warning in September.
The changes, which will see the companies drop to the FTSE 250, will take effect on Monday 20 March.
Only 30 of the original FTSE 100 from 1984 still remain in the index.