Internal conversion coefficients were measured by observing with a well-type Nal(Tl) crystal the photon spectra emitted during the de-excitation from the first excited state to the ground state of Gd^l54,D)y ¹⁶⁰, Yb^l70, Yb^l71 and Pr^l41 following the respective beta decays of Eu^l54, Tb^l60, Tm¹⁷⁰, Tm^l71 and Ce^l41. The results were obtained by analysis of either the singles spectra, or spectra obtained by coincidence-sum techniques, or both. For the coincidence work gating was done either with high energy gamma rays or with beta particles. The spectra from the Yb isotopes were analyzed on a computer using a least-squares curve-fitting program. The photon detection efficiencies, necessary for the measurements, were calculated with a computer by performing numerical integrations. The following K-shell internal conversion coefficients were measured directly for first excited state to ground state transitions: 0.632 ± 0.016, for Gd^l54; 1.48 ± 0.05, for Yb^l70; 6.9:1: 1.0, for Yb^l71 and 0. 375 ± 0. 009, for Pr^l41. The total internal conversion coefficients were measured for the first excited state to ground state transitions in Gd^l54 and nyl60 and found to be 1. 20 ± 0. 02 and 4. 52± 0. 11, which yield respective K-shell internal conversion coefficients of 0. 637 ± 0. 016 and 1. 54± 0. 06 when multiplied by K to total ratios. The results for these 2+->0+ transitions in Gd^l54 and Dy^l60 and for this -t -forbidden Ml transition in Pr^l41 are in good agreement with theory. The ratio of the experimental result to the theoretical value is 1. 09 ± 0. 06 for this 2+-0+ transition in Yb^{l 70}. The result for this Ml + E2 transition in Yb^l71 implies a mixing ratio of E2/Ml = 0. 45 :±. 0. 09, assuming the theoretical internal conversion coefficients are correct.