Cosmological Parameters and the case for Cold Dark Matter

Determinations of the main cosmological parameters are reviewed and the implications for cold dark matter discussed. There is no longer an age problem for an ${\mathrm{\Omega }}_o=1,\mathrm{\Lambda }=0$ model and, if anything, there is now an age problem for low ${\mathrm{\Omega }}_o,\mathrm{\Lambda }>0$ models. Large scale structure and CMB fluctuation data are best fitted by a mixed dark matter ${\mathrm{\Omega }}_o$ = 1 universe. Difficulties for this model with cluster evolution, the baryon content of clusters, high z Lyman $\alpha$ galaxies, and the evidence from Type Ia supernovae favouring low ${\mathrm{\Omega }}_o,\mathrm{\Lambda }>0$ models, are discussed critically.