The US stock market is currently exhibiting valuations and concentration levels that rival or exceed those seen during the 2000 Dot-Com Bubble. The S&P 500's forward price-to-earnings (P/E) ratio has risen to 22x, the highest in five years and one of the most expensive levels outside of 2020. The Technology, Media, and Telecom (TMT) sector trades at nearly 27x forward P/E, the highest since the Dot-Com Bubble burst, with the IT sector in the MSCI World index also hitting a 27x forward P/E ratio, placing it in the top 10% of the most expensive readings in two decades. Growth stocks trade near historical extremes at 26x forward P/E. US technology stocks have outperformed the broader market by the largest margin since the 2000 peak, with the Nasdaq outperforming the Russell 2000 by over 9 times, a record high. The tech sector now comprises 34.45% of the S&P 500, matching the Dot-Com Bubble peak, and the top 10% of US stocks account for a record 76% of the total market capitalization, surpassing pre-Great Depression levels and the 2000 bubble peak. Nvidia and Microsoft alone represent about 15% of the S&P 500's market cap, with Nvidia holding the largest individual stock weight in the index's history at over 8%. The top 10 stocks make up 40% of the S&P 500 market cap, driving nearly all recent growth, while the bottom 490 stocks have shown minimal gains. Various valuation metrics including trailing P/E, Shiller P/E, price-to-book, price-to-sales, EV/EBITDA, Q ratio, and market cap to GDP ratio are at historic highs, exceeding levels seen before the Great Depression and the 2000 bubble. The share of MSCI World stocks trading above 10x EV/sales has doubled in two years, surpassing the Dot-Com peak. Overall, the market's extreme concentration and elevated valuations highlight elevated risk levels reminiscent of past market bubbles.