The longitudinal nuclear relaxation of ¹⁶⁵Ho as a dilute substituent in the ferromagnetic hosts Gd, Tb and Dy has been studied by the spin echo method at liquid helium temperatures. The data have been interpreted on the basis of the Weger mechanism for the passage of nuclear magnetic energy to the conduction electrons via spin waves. The relaxation rates are found to be proportional to temperature; the nuclear magnetisation recovery follows a superposition of seven exponential functions with time constants ranging from about 1 to 30 mu s at 4.2K. The relaxation rates of Ho in Gd are found to differ by a factor of two when the direction of the Gd host magnetisation is changed by doping with Tb and Dy. The results are compared with earlier measurements on the pure metals Tb and Dy.