Landau's mean field theory of critical phenomena is corrected to take fluctuations into account. It is shown that fluctuations of intermediate wavelengths are the crucial effect producing non‐classical exponents (intermediate wavelengths are much larger than the range of forces, much smaller than the correlation length). A simple‐minded analysis of these fluctuations produces improved exponents for spatial dimension d less than 4. The exponents have an expansion in ε = d −4 . The Landau theory is the 0th order term; the terms of order ε give better agreement with experiment than Landau theory. Terms of order ε2 have been calculated using a more sophisticated theory.