The first measurements of the microwave surface resistance at 18 GHz of bulk Tl‐Ba‐Ca‐Cu‐O superconductors produced by the hot isostatic pressing (HIP) process are reported. The superconducting samples, prepared by solid‐state reaction with subsequent sintering and consolidation to obtain ideal density, were measured by replacing the end wall of a TE011circular mode gold‐plated copper cavity with the sample and determining the cavityQfor the temperature range 4–300 K. Results indicated that HIP samples which underwent subsequent annealing exhibit, below the critical temperature, a surface resistance approaching an order of magnitude less than copper.