Some investors love it when top stocks take a tumble as they see it as an opportunity to bag a bargain. These three FTSE 100 companies have all seen their share prices fall lately. Should you grab them while they’re cheap?

Aviva fever

I haven’t been enjoying the troubles afflicting insurer Aviva (LON: AV), because it’s one of the biggest holdings in my portfolio. Performance has been a bit rubbish lately, with the share price down 15% over the past two years. That was a disappointment, because the company finally looked like it had got its act together.

Chief executive Mark Wilson began well by slashing internal debt, offloading non-core and underperforming assets, and dead-heading middle management. He also drove sales growth across the UK, Turkey and Asia, offsetting eurozone setbacks. Wilson has also slotted in acquisition Friends Life pretty seamlessly, and delivered a 20% increase in full-year operating profit to £2.67bn in 2015. However, Aviva has been hit by volatile stock markets, and negative sentiment on financials generally. At a forecast valuation of nine times earnings and prospective yield of 5.3% now looks a great entry point, but be warned, I’ve said that before.

Pru in a stew

Asia-focused insurer Prudential (LSE: PRU) was turning into a two-bagger for me until it hit a sticky patch, with the share price falling 16% in the last year. Yet it also delivered a successful full-year performance, with a 22% rise in operating profit and a 20% increase in new business profit at constant exchange rates. Again, the wider fall in economic sentiment is to blame, particularly in Asia. Prudential’s emerging markets exposure was supposed to be its big strength, but lately it has become a weakness.

Loss of confidence in the US and UK, where the Pru still generates two thirds of its profits, have hurt its US retirement business and fund management arm M&G. I still believe in Pru and the long-term Asia story as the expanding middle class looks to insurance and investments to secure its newfound wealth. Prudential’s forecast valuation of 11.9 times earnings is undemanding, the stock is cheaper than it was, and I expect it to achieve two and then three-bagger status for me in due course. 

Shire ain’t higher

Specialist biopharmaceutical company Shire (LSE: SHP) enjoyed a storming run but it has stumbled lately, its share price falling 20% over the past 12 months. The revival may have already begun, helped by a 17% rise in first-quarter revenues to £1.7bn. Sales, earnings and EPS growth all posted double-digit growth, as did sales of leading treatments Vyvanse, Lialda/Mezavant and Cinryze

While short-term performance is strong, the longer-term worry is that it faces a steep patent cliff in four or five years time. It therefore needs to invest heavily in replenishing its drug pipeline, hence the £22bn takeover of Illinois-based Baxalta. This will bring treatments for rare blood conditions, cancers and immune system disorders, as well as generating $500m of cost savings over three years, a target many analysts reckon is over-optimistic.

Investors face the added uncertainty of bolting on a major acquisition which brings the added risk of extra leveraging, but brokers remain bullish and Shire could be set for another winning run.

All three could make attractive long-term buy-and-holds but first you should check out the alternatives.

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Harvey Jones owns shares of Aviva and Prudential. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.