Investment firm 3i Infrastructure said the market environment for infrastructure investment is improving and added that its portfolio is performing well and continues to deliver a good yield.The group invested £73.3m in the period from 1 April 2009 to 29 March 2010 and realised £25m. The company had cash balances of £310.6m at 29 March and no borrowings. Chairman Peter Sedgwick said: "3i Infrastructure's portfolio continues to perform well operationally and financially, generating a good yield. We expect growth in the underlying profitability of the company's equity investments year on year." "We are seeing a clear improvement in conditions for infrastructure investment, with a more favourable macroeconomic outlook, stabilising asset prices and more realistic price expectations among vendors. Consequently, the number of investment opportunities available to 3i Infrastructure is increasing," Cressida Hogg, managing partner, Infrastructure, added.