The curing reaction of four synthezized and five commercial unsaturated polyester resins were characterized by low-resolution pulse H-1-NMR and rheological measurements. The rheological measurements were done both by steady shearing flow and oscillatory shearing flow measurements. For the synthesized resins, which did not contain any inhibiting, these methods were quite comparable when measuring the gel time. Differences in measured gel times could be seen in the commercial resins. We concluded that the time taken from low-resolution pulse 1H-NMR measurements was not actually the gel time, but the time at which the resins go from the microgel formation stage to the transition stage.