A compact triple-band H-shaped slot antenna fed by microstrip coupling is proposed. Four resonant modes are excited, including a monopole mode, a slot mode, and their higher-order modes, to cover GPS (1.575 GHz) and Wi-Fi (2.4-2.485 GHz and 5.15-5.85 GHz), respectively. Sensitivity study of the slot geometry upon the resonant modes have been conducted. The measured gains at these four resonant frequencies are 0.2 dBi, 3.5 dBi, 2.37 dBi, and 3.7 dBi, respectively, and the total efficiencies are -2.5 dB, -1.07 dB, -3.06 dB, and -2.7 dB, respectively. The size of this slot antenna is only 0.24λ0×0.034λ0, where λ0 is the free-space wavelength at 1.575 GHz, hence is suitable to install on notebook PC's and handheld devices.