Costco (COST), Eli Lilly (LLY), Royal Dutch Shell (RDS) and Walmart (WMT) were among some of the widely held stocks upgraded by Louis Navellier in his latest fundamental stock analysis on April 12, 2010.

Warehouse retailer Costco (COST) last week reported net sales of $7.14 billion for March, up 12% from $6.40 billion last year. The improvement in fundamentals helped the stock get upgraded from a a C grade or “sell” in Portfolio Grader to a B grade or “buy” this week. Costco stock was downgraded by Louis Navellier on March 29, but has bounced back quickly.

Pharmaceutical stock Eli Lilly (LLY) has been showing strength since a federal judge upheld one of the patents protecting its blockbuster cancer treatment Gemzar on April 1.The stock was upgraded from a D grade or “sell” last week to a C grade or “hold” this week in Louis Navellier’s database of stocks to buy and sell.

Energy stock Royal Dutch Shell (RDS) announced today that it will in fact be exiting the retail business in 21 African nations, but speculation on this move started to form early last week and helped bolster Shell stock shares. As a result of this company news, the stock was upgraded from a D grade or “sell” last week to a C grade or “hold” this week

Walmart (WMT), has been cutting grocery sales to lure back customers, and Walmart stock has been improving as a result. The stock was upgraded from a D grade or “sell” last week to a C grade or “hold” this wee in Portfolio Grader’s fundamental stock analysis.

About Portfolio Grader: Every Sunday, renowned growth stock adviser Louis Navellier runs a fundamental analysis on the top 5,000 Wall Street companies. Armed with this research, Navellier offers a rating for each company reflected as  a simple letter grade, with A being “strong buy” and F being “strong sell.” Portfolio Grader’s stock data is free and open to the public, and can be accessed online here.