Doppler-free laser-fluorescence and laser-rf double-resonance studies have been made of the hyperfine structure (hfs) of four strong, previously unclassified visible lines in Ho i; all are shown to connect with low levels. The hfs of the 4f116s24I11/2,9/2 levels is measured in detail, allowing evaluation of the dipole (a01, a12, a10) and quadrupole (b02, b11, b13) hfs radial integrals. The results are in close agreement with the ab initio values of Lindgren Rosen [ Case Stud. Atom. Phys.4, 93– 292 ( 1974)]. The value found for b02 in the 4f116s2 configuration is in reasonable agreement with that of Wyart Camus [ Physica93C, 227– 236 ( 1978)], thereby confirming their finding of a substantial dependence of this parameter on the number of 4f electrons in the core.