August was a great month for CSL Ltd (ASX: CSL) shares.
Not to mention the company's shareholders.
In the month just past, the S&P/ASX 200 Index (ASX: XJO) gained a respectable 1.1%.
But the Aussie biotech giant left those gains in the dust.
Indeed, on 31 July, you could have bought CSL shares at market close for $123.06. When the closing bell sounded on 31 August, those shares were swapping hands for $171.57 apiece.
This put the ASX 200 biotech stock up a whopping 39.4% in August.
And this isn't some microcap stock we're talking about here. CSL commands a market cap of nearly $84 billion.

Image source: Getty Images
What sent CSL shares soaring in August?
At the beginning of August, the CSL share price was down more than 53% over the previous 12 months.
With investors seemingly sensing that the company's 'reset' process is gaining traction, bargain hunters sent shares in the ASX 200 biotech up 9.4% by market close on 17 August.
Then, on 18 August, CSL announced its FY 2026 results.
Now, full year revenue of US$15.8 billion was down 1% from FY 2025. However, that significantly beat the company's revised guidance (issued in May) of US$15.2 billion.
And CSL also operated at a loss, with reported net profit after tax (NPAT) coming in at a loss of US$2.6 billion.
Still, management declared an unfranked final dividend of $2.277 a share, down 7% from last year's final dividend in Aussie dollar terms.
That passive income payout is still up for grabs, by the way. If you want to bank the final CSL dividend, you'll need to own shares at market close on 8 September. You can then expect to get paid on 2 October.
So, why did CSL shares surge 17.3% on the day of the results release?
That looks to have been driven by expectations of a stronger year (and years) ahead.
"FY26 has been a year of reset. We have taken decisive action and created a clear path to return to sustainable growth," CSL interim CEO Gordon Naylor said.
The ASX 200 biotech stock forecasts steady revenue in FY 2027, while it expects underlying NPAT to grow by around 5%.
Is it too late to buy the ASX 200 biotech stock today?
Despite the big surge in CSL shares in recent months, Morgans' Damien Nguyen believes the ASX 200 biotech stock remains an appealing investment (courtesy of The Bull).
According to Nguyen, who issued a buy recommendation on CSL:
CSL is a global healthcare leader with strong competitive advantages across plasma therapies, vaccines and specialty medicines. Demand for its products remain largely independent of economic conditions.
Nguyen added:
In our view, the latest full year result in 2026 is generating confidence that repeated earnings downgrades are behind CSL.
With defensive earnings, global market leadership and attractive long term growth prospects, we view CSL as an appealing investment opportunity.