We have determined effective collision strengths for fine-structure tr
ansitions among the 2s(2)2p2 and 2s2p3 configurations of seven ions in
the C I isoelectronic sequence, by interpolating or extrapolating fro
m data calculated by the R-matrix method for the C-like species Si IX,
Ca XV and Fe XXI. We present the results as coefficients to polynomia
l fits which may be used to estimate the effective collision strengths
to an accuracy of +/- 20%.