Plasmodium mexicanum, a malaria parasite of lizards, exhibits substantial variation among infections in the life–history traits which define its blood–dwelling stages. Such variation in life histories among infections is common in Plasmodium and may influence the ecology and evolution of the parasite's transmission success and virulence. Insight into these issues requires identification of independent traits (some traits may be bound by developmental trade–offs) and the importance of genetic versus host effects producing the variation. We studied 11 life–history traits in 120 induced infections of P . mexicanum in its natural lizard host (20 each from six donor infections). The traits varied among infections and fell into three clusters: rate/peak (rate of increase and peak parasitaemia of asexuals and gametocytes), time (duration of pre–patent period and the infection's growth) and maturity (timing of first gametocytes). Thus, few life–history traits define an infection in the lizard's blood. Donor effects were significant for ten traits and two trait clusters (maturity was the exception) suggesting genetic differences among infections may influence the rate of increase and peak parasitaemia, but not the timing of the first production of gametocytes.