Recombination spectra have been calculated for H I , He II and the 2 p – nd series of He I . Expressions are given for the calculation of He +2 /H + and He + /H + abundance ratios. It is shown that the ionized region of a nebula will contain a negligible amount of neutral helium if I (He II , λ 4686)/ I (He I , λ 5876) exceeds 1.2. For NGC 7662 and 2392 the measured relative intensities within each spectrum are in good agreement with theory but for NGC 7027 the agreement is poor for the weak lines and for the infra-red. The suggestion that the intensity anomalies for NGC 7027 may be due to collisional processes is found to be difficult to accept. The possibility is considered that there may be systematic errors in the intensity measurements. The He/H abundance ratios, by numbers of atoms, are found to be 0.20 for NGC 7662, 0.16 for NGC 2392 and 0.19 for NGC 7027.