Constraining warm inflation with the cosmic microwave background

We discuss the spectrum of scalar density perturbations from warm inflation when the friction coefficient Γ in the inflaton equation is dependent on the inflaton field. The spectral index of scalar fluctuations depends on a new slow-roll parameter constructed from Γ. A numerical integration of the perturbation equations is performed for a model of warm inflation and gives a good fit to the WMAP data for reasonable values of the model's parameters.